Phosphor composition and method for producing the same, and light-emitting device using the same

ABSTRACT

A light-emitting device is produced using a phosphor composition containing a phosphor host having as a main component a composition represented by a composition formula: aM 3 N 2 .bAlN.cSi 3 N 4 , where “M” is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and “a”, “b”, and “c” are numerical values satisfying 0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, and 0.4≦c/(c+a)≦0.95. This enables a light-emitting device emitting white light and satisfying both a high color rendering property and a high luminous flux to be provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 11/891,386,filed Aug. 10, 2007 and issued as U.S. Pat. No. 7,507,354 on Mar. 24,2009, which is a Continuation of application Ser. No. 11/568,149, filedOct. 20, 2006 and issued as U.S. Pat. No. 7,391,060 on Jun. 24, 2008,which is a U.S. National Stage application of International ApplicationNo. PCT/JP2005/008395, filed Apr. 26, 2005, which applications areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a novel phosphor composition applicableto various kinds of light-emitting devices such as a whitelight-emitting diode (hereinafter, referred to as a “white LED”). Inparticular, the present invention relates to a phosphor composition thatis excited with near-ultraviolet light, violet light, or blue light toemit light in a warm color such as orange or red and a method forproducing the phosphor composition, and a light-emitting device usingthe phosphor composition.

BACKGROUND ART

Conventionally, for example, the following nitride phosphors have beenknown. These nitride phosphors can be excited with ultravioletlight-near-ultraviolet light-violet light-blue light, and emit visiblelight in a warm color having an emission peak in a wavelength range of580 nm to less than 660 nm. Therefore, these nitride phosphors also havebeen known to be suitable for a light-emitting device such as a whiteLED light source.

(1) M₂Si₅N₈:Eu²⁺ (see JP 2003-515665 A)

(2) MSi₇N₁₀:Eu²⁺ (see JP 2003-515665 A)

(3) M₂Si₅N₈:Ce³⁺ (see JP 2002-322474 A)

(4) Ca_(1.5)Al₃Si₉N₁₆:Ce³⁺ (see JP 2003-203504 A)

(5) Ca_(1.5)M₃Si₉N₁₆:Eu²⁺ (see JP 2003-124527 A)

(6) CaAl₂Si₁₀N₁₆:Eu²⁺ (see JP 2003-124527 A)

(7) Sr_(1.5)Al₃Si₉N₁₆:Eu²⁺ (see JP 2003-124527 A)

(8) MSi₃N₅:Eu²⁺ (see JP 2003-206481 A)

(9) M₂Si₄N₇:Eu²⁺ (see JP 2003-206481 A)

(10) CaSi₆AlON₉:Eu²⁺ (see JP 2003-206481 A)

(11) Sr₂Si₄AlON₇:Eu²⁺ (see JP 2003-206481 A)

(12) CaSiN₂:Eu²⁺ (see S. S. Lee, S. Lim, S. S. Sun and J. F. Wager,Proceedings of SPIE—the International Society for Optical Engineering,Vol. 3241 (1997), pp. 75-83)

In the above phosphors, “M” represents at least one alkaline-earth metalelement (Mg, Ca, Sr, Ba), or zinc (Zn).

Conventionally, such nitride phosphors have been produced mainly by thefollowing production method: a nitride of the element “M” or metal, anda nitride of silicon and/or a nitride of aluminum are used as materialsfor a phosphor host, and they are allowed to react with a compoundcontaining an element that forms a luminescent center ion in a nitridinggas atmosphere. Furthermore, a conventional light-emitting device hasbeen configured using such a nitride phosphor.

However, because the request for the above-mentioned light-emittingdevice is being diversified year after year, there is a demand for anovel phosphor different from the above-mentioned conventional nitridephosphor. In particular, there is a great demand for a light-emittingdevice containing a large amount of the above-mentioned light-emittingcomponent in a warm color, above all, a red light-emitting component,and there is a strong demand for the development of such alight-emitting device. However, actually, only a small number ofphosphor ingredients are available, so that there is a need fordeveloping a novel phosphor ingredient and a novel light-emitting devicecontaining a large amount of light-emitting component in a warm color.

Furthermore, according to the conventional method for producing anitride phosphor, it is difficult to obtain and produce a high-puritymaterial, and a nitride phosphor is produced using, as a main material,a nitride of alkaline-earth metal, alkaline-earth metal, or the like,which is difficult to handle in the atmosphere due to its chemicalinstability. Therefore, it is difficult to mass-produce a high-purityphosphor, reducing the production yield, which increases the cost of aphosphor.

Furthermore, in the conventional light-emitting device, there is only asmall number of kinds of applicable phosphor ingredients. Therefore,there is no room for selecting a material, and a manufacturer thatsupplies a phosphor is limited. Consequently, a light-emitting devicebecomes expensive. Furthermore, there is a small number of kinds ofinexpensive light-emitting devices with a high emission intensity of alight-emitting component in a warm color (in particular, red) and with alarge special color rendering index R9.

The present invention has been achieved in order to solve theabove-mentioned problems, and its object is to provide a novel phosphorcomposition capable of emitting light in a warm color, in particular, aphosphor composition emitting red light. Another object of the presentinvention is to provide a method for producing a phosphor compositionthat can be produced at a low cost, suitable for mass-production of thenitride phosphor composition according to the present invention. Stillanother object of the present invention is to provide an inexpensivelight-emitting device with a high emission intensity of a light-emittingcomponent in a warm color (in particular, red) and with a large specialcolor rendering index R9.

Regarding the technique of measuring the internal quantum efficiency andthe external quantum efficiency of a phosphor according to the presentinvention, a technique capable of conducting measurement with highprecision already has been established. Regarding a part of phosphorsfor a fluorescent lamp, absolute values of the internal quantumefficiency and the external quantum efficiency under the irradiation oflight (excitation with ultraviolet light of 254 nm) with a particularexcitation wavelength are known (e.g., see “Publication of IlluminatingEngineering Institute of Japan” by Kazuaki Ohkubo et al., 1999, Vol. 83,No. 2, p. 87).

DISCLOSURE OF INVENTION

The present invention is directed to a phosphor composition containing aphosphor host having as a main component a composition represented by acomposition formula: aM₃N₂.bAlN.cSi₃N₄, where the “M” is at least oneelement selected from the group consisting of Mg, Ca, Sr, Ba, and Zn,and “a”, “b”, and “c” are numerical values respectively satisfying0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, and 0.4≦c/(c+a)≦0.95.

Furthermore, the present invention is directed to a light-emittingdevice configured using the above-mentioned phosphor composition as alight-emitting source.

Furthermore, the present invention is directed to a method for producingthe above-mentioned phosphor composition including allowing a material,which contains a compound capable of generating an oxide of at least oneelement selected from the group consisting of Mg, Ca, Sr, Ba, and Zn byheating, a silicon compound, an aluminum compound, a compound containingan element forming a luminescent center ion, and carbon, to react in anitriding gas atmosphere.

Furthermore, the present invention is directed to a light-emittingdevice including a phosphor layer containing a nitride phosphor and alight-emitting element, the light-emitting element having an emissionpeak in a wavelength range of 360 nm to less than 500 nm, the nitridephosphor being excited with light emitted by the light-emitting elementto emit light, and the light-emitting device containing at leastlight-emitting component light emitted by the nitride phosphor as outputlight. The nitride phosphor is activated with Eu²⁺ and is represented bya composition formula: (M_(1-x)Eu_(x))AlSiN₃, and the “M” is at leastone element selected from the group consisting of Mg, Ca, Sr, Ba, andZn, and the “x” is a numerical value satisfying 0.005≦x≦0.3.

Furthermore, the present invention is directed to a light-emittingdevice including a phosphor layer containing a phosphor and alight-emitting element, the light-emitting element having an emissionpeak in a wavelength range of 360 nm to less than 500 nm, the phosphorbeing excited with light emitted by the light-emitting element to emitlight, and the light-emitting device containing at least light-emittingcomponent light emitted by the phosphor as output light. The phosphor isactivated with Eu²⁺ and contains a nitride phosphor or an oxynitridephosphor having an emission peak in a wavelength range of 600 nm to lessthan 660 nm, and an alkaline-earth metal orthosilicate phosphoractivated with Eu²⁺ and having an emission peak in a wavelength range of500 nm to less than 600 nm. An internal quantum efficiency of thephosphor is at least 80% under the excitation with light emitted by thelight-emitting element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor light-emittingdevice in an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor light-emittingdevice in an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor light-emittingdevice in an embodiment of the present invention.

FIG. 4 is a schematic view showing a configuration of anillumination•display device in the embodiment of the present invention.

FIG. 5 is a schematic view showing a configuration of anillumination•display device in the embodiment of the present invention.

FIG. 6 is a perspective view of an illumination module in the embodimentof the present invention.

FIG. 7 is a perspective view of an illumination module in the embodimentof the present invention.

FIG. 8 is a perspective view of an illumination device in the embodimentof the present invention.

FIG. 9 is a side view of an illumination device in the embodiment of thepresent invention.

FIG. 10 is a bottom view of the illumination device shown in FIG. 9.

FIG. 11 is a perspective view of an image display device in theembodiment of the present invention.

FIG. 12 is a perspective view of a number display device in theembodiment of the present invention.

FIG. 13 is a partial cut-away view of an end portion of a fluorescentlamp in the embodiment of the present invention.

FIG. 14 is a cross-sectional view of an EL panel in the embodiment ofthe present invention.

FIG. 15 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 1 of the presentinvention.

FIG. 16 is a diagram showing an X-ray diffraction pattern of thephosphor composition in Example 1 of the present invention.

FIG. 17 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 2 of the presentinvention.

FIG. 18 is a diagram showing an X-ray diffraction pattern of thephosphor composition in Example 2 of the present invention.

FIG. 19 is a diagram showing an emission spectrum of a phosphorcomposition related to Example 2 of the present invention.

FIG. 20 is a diagram showing the relationship between an Eu replacementamount and an emission peak wavelength of the phosphor compositionrelated to Example 2 of the present invention.

FIG. 21 is a diagram showing the relationship between an Eu replacementamount and an emission intensity of the phosphor composition related toExample 2 of the present invention.

FIG. 22 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 3 of the presentinvention.

FIG. 23 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 4 of the presentinvention.

FIG. 24 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 5 of the presentinvention.

FIG. 25 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 6 of the presentinvention.

FIG. 26 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 7 of the presentinvention.

FIG. 27 is a diagram showing an emission spectrum and an excitationspectrum of a phosphor composition in Example 8 of the presentinvention.

FIG. 28 is a ternary system of composition showing a composition rangeof the phosphor composition of the present invention.

FIG. 29 shows emission characteristics of a SrSiN₂:Eu²⁺ red phosphor.

FIG. 30 shows emission characteristics of a SrAlSiN₃:Eu²⁺ red phosphor.

FIG. 31 shows emission characteristics of a Sr₂Si₅N₈:Eu²⁺ red phosphor.

FIG. 32 shows emission characteristics of a (Ba, Sr)₂SiO₄:Eu²⁺ greenphosphor.

FIG. 33 shows emission characteristics of a (Sr, Ba)₂SiO₄:Eu²⁺ yellowphosphor.

FIG. 34 shows emission characteristics of a (Sr, Ca)₂SiO₄:Eu²⁺ yellowphosphor.

FIG. 35 shows emission characteristics of a 0.75CaO.2.25 AlN.3.25Si₃N₄:Eu²⁺ yellow phosphor.

FIG. 36 shows emission characteristics of a (Y, Gd)₃Al₅O₁₂:Ce³⁺ yellowphosphor.

FIG. 37 shows emission characteristics of a BaMgAl₁₀O₁₇:Eu²⁺ bluephosphor.

FIG. 38 shows emission characteristics of a Sr₄Al₁₄O₂₅:Eu²⁺ blue-greenphosphor.

FIG. 39 shows emission characteristics of a (Sr, Ba)₁₀(PO₄)₆Cl₂:Eu²⁺blue phosphor.

FIG. 40 shows emission characteristics of a La₂O₂S:Eu³⁺ red phosphor.

FIG. 41 is a perspective view of a light-emitting device in Example 26of the present invention.

FIG. 42 a partial cross-sectional view of the light-emitting device inExample 26 of the present invention.

FIG. 43 shows an emission spectrum of the light-emitting device inExample 26 of the present invention.

FIG. 44 shows an emission spectrum of the light-emitting device inComparative Example 6 of the present invention.

FIG. 45 shows results obtained by simulating the relationship betweenthe correlated color temperature and the relative luminous flux inExample 26 and Comparative Example 6 of the present invention.

FIG. 46 shows results obtained by simulating the relationship betweenthe correlated color temperature and Ra in Example 26 and ComparativeExample 6 of the present invention.

FIG. 47 shows results obtained by simulating the relationship betweenthe correlated color temperature and Ra in Example 27 of the presentinvention.

FIG. 48 shows results obtained by simulating the relationship betweenthe correlated color temperature and R9 in Example 27 of the presentinvention.

FIG. 49 shows results obtained by simulating the relationship betweenthe correlated color temperature and the relative luminous flux inExample 27 of the present invention.

FIG. 50 shows an emission spectrum of the light-emitting device inExample 27 of the present invention.

FIG. 51 shows an emission spectrum of the light-emitting device inExample 28 of the present invention.

FIG. 52 shows an emission spectrum of the light-emitting device inComparative Example 7 of the present invention.

FIG. 53 shows results obtained by simulating the relationship betweenthe correlated color temperature and the relative luminous flux inExample 28 and Comparative Example 7 of the present invention.

FIG. 54 shows results obtained by simulating the relationship betweenthe correlated color temperature and the relative luminous flux of thelight-emitting device using an ideal phosphor in Example 28 andComparative Example 7 of the present invention.

FIG. 55 shows results obtained by simulating the relationship betweenthe correlated color temperature and Ra in Example 28 and ComparativeExample 7 of the present invention.

FIG. 56 shows results obtained by simulating the relationship betweenthe correlated color temperature and R9 in Example 28 and ComparativeExample 7 of the present invention.

FIG. 57 shows results obtained by simulating an emission spectrum of thelight-emitting device emitting white light in a warm color at acorrelated color temperature of 4500 K (duv=0) in Example 28 of thepresent invention.

FIG. 58 shows results obtained by simulating an emission spectrum of thelight-emitting device emitting white light in a warm color at acorrelated color temperature of 5500 K (duv=0) in Example 28 of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described by way ofembodiments.

Embodiment 1

First, an embodiment of a phosphor composition of the present inventionwill be described. An example of the phosphor composition of the presentinvention contains a phosphor host and a luminescent center ion, andcontains, as a main component of the phosphor host, a compositionrepresented by a composition formula: aM₃N₂.bAlN.cSi₃N₄, where “M” is atleast one element selected from the group consisting of Mg, Ca, Sr, Ba,and Zn, and “a”, “b”, and “c” are numerical values respectivelysatisfying 0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, 0.4≦c/(c+a)≦0.95. Whensuch a composition is used as the phosphor host, for example, in thecase where an Eu²⁺ ion are added as a luminescent center, the phosphorcomposition becomes a phosphor that is excited with ultraviolet light,near-ultraviolet light, violet light, or blue light to emit light in awarm color such as orange or red.

Herein, containing a composition as a main component refers tocontaining a composition in an amount exceeding 50% by weight,preferably at least 75% by weight, and more preferably at least 85% byweight.

The above-mentioned “a”, “b”, and “c”, which are preferable in terms ofthe emission efficiency and the color tone of emitted light, arenumerical values satisfying 0.2≦a/(a+b)≦0.6, 0.3≦b/(b+c)≦0.8,0.4≦c/(c+a)≦0.8, more preferably 0.2≦a/(a+b)≦0.3, 0.6≦b/(b+c)≦0.8,0.4≦c/(c+a)≦0.6.

The above-mentioned phosphor host may be a composition represented by acomposition formula: MAlSiN₃.

Another example of the phosphor host of the present invention does notcontain a composition represented by a composition formula: M₂Si₅N₈,MSi₇N₁₀, M_(1.5)Al₃Si₉N₁₆, MAl₂Si₁₀N₁₆, MSi₉N₅, M₂Si₄N₇, MSi₆AlON₉,M₂Si₄AlON₇, or MSiN₂, and is generated by firing a mixed material, inwhich at least one nitride selected from a nitride of akaline-earthmetal and a nitride of zinc, europium oxide, silicon nitride, and anitride of aluminum are mixed in a molar ratio of2(1−x):3×:2:6(0<x<0.1), in nitrogen-hydrogen mixed gas at 1600° C. for 2hours.

The element “M”, which is preferable in terms of the emission efficiencyand the color tone of emitted light, is at least one element selectedfrom Ca and Sr, and the main component of the element “M” preferably isCa or Sr for the purpose of obtaining a phosphor emitting red light withsatisfactory purity. The element “M” also may be configured as a mixtureof at least two elements among the above-mentioned group of elements.

Setting the main component of the element “M” to be Ca or Sr refers tosetting a large majority, preferably, at least 80 atomic % of theelement “M” to be Ca or Sr. Furthermore, the composition preferable interms of the material management and production is the one in which allthe elements “M” are set to be one element among the above-mentionedgroup of elements, for example, all the elements “M” are set to be Ca orSr.

Furthermore, it is preferable that the composition represented by theabove-mentioned composition formula: MAlSiN₃ contains a compoundrepresented by the above-mentioned chemical formula: MAlSiN₃, and it ismore preferable that the composition contains the above-mentionedcompound as a main component. Although it is preferable that thephosphor composition of the present embodiment does not containimpurity, the phosphor composition may contain, for example, at leastone of a metal impurity element and a gasifiable impurity element in anamount corresponding to less than 10 atomic % with respect to at leastone of the elements “M”, Al, Si, and N. Furthermore, in the case wherethe composition is a compound represented by the above-mentionedchemical formula: MAlSiN₃, even if there is an excess or deficiency inAl, Si, or N in the above-mentioned chemical formula: MAlSiN₃ in a rangenot exceeding 10 atomic %, the phosphor host only needs to contain, as amain component, a compound represented by the chemical formula: MAlSiN₃.More specifically, for the purpose of slightly improving the emissionperformance of a phosphor, a trace amount or small amount of impuritycan be added, or a composition slightly shifted from a stoichiometriccomposition can be used.

For example, in order to slightly improve the emission performance, inthe phosphor composition of the present embodiment, a part of Si alsocan be replaced by at least one element such as Ge or Ti capable oftaking a quadrivalent state, and a part of Al also can be replaced by atleast one element such as B, Ga, In, Sc, Y, Fe, Cr, Ti, Zr, Hf, V, Nb,or Ta capable of taking a trivalent state. Herein, “a part” refers tothat the atomic number with respect to Si or Al is less than 30 atomic%, for example.

The substantial composition range of the above-mentioned composition ispresented by MAl_(1±0.3)Si_(1±0.3)N_(3(1±0.3))O_(0-0.3), preferablyMAl_(1±0.1)Si_(1±0.1)N_(3(1±0.1))O_(0-0.1.)

Furthermore, it is preferable that the above-mentioned composition isrepresented by, in particular, a composition formula or a chemicalformula: SrAlSiN₃ or CaAlSiN₃. For example, the composition may have aplurality of alkaline-earth metal elements, such as (Sr, Ca)AlSiN₃, (Sr,Mg)AlSiN₃, (Ca, Mg)AlSiN₃, or (Sr, Ca, Ba)AlSiN₃. In the abovecomposition formula, O (oxygen) is an impurity element that enters aphosphor composition in the course of production thereof.

A phosphor composition is configured by adding at least one of ions tobe a luminescent center (luminescent center ion) to the crystal latticeof a compound constituting the phosphor host. When a luminescent centerion is added to the phosphor host, a phosphor emitting fluorescence isobtained.

As the luminescent center ion, a metal ion can be appropriately selectedfrom various kinds of rare-earth ions and transition metal ions.Specific examples of the luminescent center ion include trivalentrare-earth metal ions such as Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺,Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, and Yb³⁺; divalent rare-earth metal ions such asSm²⁺, Eu²⁺, and Yb²⁺; divalent rare-earth metal ions such as Mn²⁺,trivalent transition metal ions such as Cr³⁺ and Fe³⁺; and quadrivalenttransition metal ions such as Mn⁴⁺.

In the phosphor composition of the present embodiment, it is preferable,in terms of the emission efficiency, that the luminescent center ion isat least one ion selected from Ce³⁺ and Eu²⁺. Furthermore, when aphosphor contains such an ion, the phosphor becomes preferable for awhite LED. When the luminescent center ion is Eu²⁺, a phosphor emittinglight in a warm color can be obtained, which is preferable for alight-emitting device, in particular, an illumination device. When theluminescent center ion is Ce³⁺, is, a phosphor emitting blue-green lightcan be obtained, which is preferable for a light-emitting device with ahigh color rendering property, in particular, an illumination device.

In the phosphor composition of the present embodiment, it is preferable,in terms of the emission color, that the luminescent center ion is atleast one ion selected from the group consisting of Ce³⁺, Eu²⁺, Eu³⁺,and Tb³⁺. When the luminescent center ion is Ce³⁺, a phosphor with ahigh efficiency emitting at least blue-green light can be obtained. Whenthe luminescent center ion is Eu²⁺, a phosphor with a high efficiencyemitting orange to red light can be obtained. When the luminescentcenter ion is Eu³⁺, a phosphor with a high efficiency emitting red lightcan be obtained. When the luminescent center ion is Tb³⁺, a phosphorwith a high efficiency emitting green light can be obtained. Any of thephosphors emit any light of red, green, or blue with a high color purityto be three primary colors, or orange that is highly demanded, so that aphosphor preferable for a light-emitting device is obtained.

The preferable addition amount of the luminescent center ion variesdepending upon the kind of the luminescent center ion. For example, inthe case where the luminescent center ion is Eu²⁺ or Ce³⁺, thepreferable addition amount of the luminescent center ion is 0.1 atomic %to 30 atomic %, preferably 0.5 atomic % to 10 atomic % with respect tothe above-mentioned element “M”. When the addition amount is larger orsmaller than the above range, a phosphor is not obtained that satisfiesboth the satisfactory emission color and the high luminance. Basically,it is preferable that the luminescent center ion is added so as toreplace a part of a lattice position of the element “M”. However, theluminescent center ion also may be added so as to replace a part of anylattice position of Al and Si.

The phosphor composition of the present embodiment also can be aphosphor with a plurality of luminescent center ions coactivated.Examples of a phosphor with luminescent center ions coactivated includea phosphor with a Ce³⁺ ion and an Eu²⁺ ion coactivated, a phosphor withan Eu²⁺ ion and a Dy³⁺ ion coactivated, a phosphor with an Eu²⁺ ion anda Nd³⁺ ion coactivated, a phosphor with a Ce³⁺ ion and a Mn²⁺ ioncoactivated, and a phosphor with an Eu²⁺ ion and a Mn²⁺ ion coactivated.Thus, a phosphor with the shapes of an excitation spectrum and anemission spectrum regulated may be obtained, using a phenomenon in whichenergy shifts from one luminescent center ion to another ion, and along-persistence phosphor with long persistence may be obtained, usingan excitation phenomenon caused by heat.

Phosphors preferable for a light-emitting device according to thepresent invention will be described below. Such phosphors can beobtained by varying the numerical values of the above-mentioned “a”,“b”, and “c”, the elements occupying the element “M”, and the kind andaddition amount of the luminescent center ion.

(1) A phosphor emitting light in a warm color, in particular, red lighthaving an emission peak in a wavelength range of 580 nm to less than 660nm, preferably 610 nm to 650 nm in terms of the color purity andspectral luminous efficacy required for a light-emitting device.

(2) A phosphor capable of being excited with the irradiation ofnear-ultraviolet light or ultraviolet light having an emission peak in awavelength range of 350 nm to less than 420 nm, preferably 380 nm toless than 410 nm in terms of the excitation characteristics required fora light-emitting device.

(3) A phosphor capable of being excited with the irradiation of bluelight having an emission peak in a wavelength range of 420 nm to lessthan 500 nm, preferably 440 nm to less than 480 nm in terms of theexcitation characteristics required for a light-emitting device.

(4) A phosphor capable of being excited with the irradiation of greenlight having an emission peak in a wavelength range of 500 nm to lessthan 560 nm.

There is no particular limit on the property of the phosphor compositionof the present embodiment. The phosphor composition may be a singlecrystal bulk, a ceramics molding, a thin film having a thickness ofseveral nm to several μm, a thick film having a thickness of several 10μm to several 100 μm, or powder. For the purpose of applying thephosphor composition to a light-emitting device, the phosphorcomposition preferably is powder, more preferably powder with a centerparticle diameter (D₅₀) of 0.1 μm to 30 μm, and most preferably powderwith a center particle diameter (D₅₀) of 0.5 μm to 20 μm. There is noparticular limit to the shape of a particle of the phosphor composition,and the particle may be any of a spherical shape, a plate shape, a barshape, and the like.

The phosphor composition of the present embodiment that can be producedas described above is capable of being excited with at least ultravioletlight-near-ultraviolet light-violet light-blue light-green light-yellowlight-orange light of 250 nm to 600 nm, and at least becomes a phosphoremitting blue-green, orange, or red light. A phosphor emitting red lighthaving an emission peak in a wavelength range of 610 nm to 650 nm alsocan be obtained. The shapes of the excitation spectrum and the emissionspectrum of a phosphor that contains an Eu²⁺ ion as a luminescent centerand emits red light are relatively similar to those of the conventionalphosphor activated with Eu²⁺ containing, as a material for a base,Sr₂Si₅N₈ nitridosilicate.

Next, a method for producing a phosphor composition of the presentembodiment will be described.

Production Method 1 of the Present Invention

The phosphor composition of the present embodiment can be produced, forexample, by the production method described below.

First; as a material for forming a phosphor host, a nitride ofalkaline-earth metal M (M₃N₂) or a nitride of zinc (Zn₃N₂), siliconnitride (Si₃N₄), and aluminum nitride (AlN) are prepared. The nitride ofalkaline-earth metal and the nitride of zinc are not those which areusually used as ceramic materials, but are those which are difficult toobtain and expensive, and are difficult to handle in the atmospheresince they easily react with water vapor in the atmosphere.

Furthermore, as a material for adding a luminescent center ion, variouskinds of rare-earth metals, transition metals, or compounds thereof areused. Such elements include lanthanide and transition metal with anatomic number of 58 to 60, or 62 to 71, in particular, Ce, Pr, Eu, Tb,and Mn. Examples of a compound containing such elements include anoxide, a nitride, a hydroxide, a carbonate, an oxalate, a nitrate, asulfate, a halide, and a phosphate of the above-mentioned lanthanide andtransition metal. Specific examples include cerium carbonate, europiumoxide, europium nitride, metallic terbium, and manganese carbonate.

Next, these phosphor ingredients are weighed and mixed so that theatomic ratio of the respective atoms becomes a(M_(1-x)Lc_(x))₃N₂.bAlN.cSi₃N₄, whereby a mixed material is obtained.Herein, “M” is at least one element selected from the group consistingof Mg, Ca, Sr, Ba, and Zn; “a”, “b”, and “c” are numerical valuessatisfying 0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, and 0.4≦c/(c+a)≦0.95; Lcrepresents an element to be a luminescent center ion; “x” represents anumerical value satisfying 0<x<0.3, preferably 0.001≦x≦0.2, and morepreferably 0.005≦x≦0.1. For example, the atomic ratio is assumed to beM_(1-x)Lc_(x)AlSiN₃.

Then, the mixed material is fired in any atmosphere of a vacuumatmosphere, a neutral atmosphere (inactive gas, nitrogen gas, etc.), anda reducing atmosphere (CO, nitrogen-hydrogen mixed gas, etc.).

As the above-mentioned atmosphere, a normal-pressure atmosphere ispreferable for the reason that simple facility can be used. However, anyof a high-pressure atmosphere, a compressed atmosphere, areduced-pressure atmosphere, and a vacuum atmosphere may be used. Thepreferable reaction atmosphere for the purpose of enhancing theperformance of a phosphor is a high-pressure atmosphere mainlycontaining nitrogen gas of, for example, 2 to 100 atm pressure,preferably 5 to 20 atm pressure in view of the handling of theatmosphere. With such a high-pressure atmosphere, the decomposition of anitride phosphor composition, which occurs during firing at hightemperature, can be prevented or suppressed, and the shift of thecomposition of a phosphor composition is suppressed, whereby a phosphorcomposition with high exhibition performance can be produced.

Furthermore, the preferable atmosphere for the purpose of generating alarge amount of ions such as Ce³⁺, Eu²⁺, Tb³⁺, or Mn²⁺, as a luminescentcenter ion, is a reducing atmosphere. The firing temperature is, forexample, 1,300° C. to 2,000° C., preferably 1,600° C. to 2,000° C. andmore preferably 1,700° C. to 1,900° C. for the purpose of enhancing theperformance of a phosphor. On the other hand, for the purpose ofmass-production, the firing temperature is preferably 1,400° C. to1,800° C., more preferably 1,600° C. to 1,700° C. The firing time is,for example, 30 minutes to 100 hours, preferably 2 to 8 hours in view ofthe productivity. Firing may be performed in different atmospheres, ormay be performed several times in the same atmosphere. The fired bodyobtained by such firing becomes a phosphor composition.

The phosphor composition of the present embodiment is not limited tothose that are produced by the above production method. The phosphorcomposition of the present embodiment also can be produced by aproduction method using, for example, a vapor phase reaction or a liquidphase reaction, as well as the above-described solid phase reaction.

It is difficult to obtain a nitride such as Si₃N₄ or AlN with a highpurity, although not comparable to the case of a nitride ofalkaline-earth metal. In most cases, the above-mentioned Si₃N₄ or AlN ispartially oxidized in the atmosphere to contain SiO₂ or Al₂O₃ andslightly decrease the purity thereof. For this reason, the phosphorcomposition of the present embodiment may be the one substantiallyhaving a composition with the above-mentioned desired atomic ratio, andin the above-mentioned composition formula: MAlSiN₃, a part of Si₃N₄ orAlN may be oxidized to some degree to contain a composition modified toSiO₂ or Al₂O₃.

Production Method 2 of the Present Invention

The phosphor composition of the present embodiment can be produced, forexample, by the production method described below.

The production method 2 of the present invention is a method forproducing a phosphor composition containing, as a main component of aphosphor host, a composition represented by the above-mentionedcomposition formula: aM₃N₂.bAlN.cSi₃N₄, in particular, MAlSiN₃. Themethod includes allowing a material, which contains a compound capableof generating an oxide of at least one element “M” selected from thegroup consisting of Mg, Ca, Sr, Ba, and Zn by heating, a siliconcompound, an aluminum compound, a compound containing an element forminga luminescent center ion, and carbon, to react in a nitriding gasatmosphere.

According to an example of the production method 2 of the presentinvention, while an alkaline-earth metal compound or a zinc compoundcapable of generating a metal oxide MO (where “M” is Mg, Ca, Sr, Ba, orZn) by heating, preferably an alkaline-earth metal compound capable ofgenerating CaO or SrO by heating, is reduced and nitrided by thereaction with carbon in a nitriding gas atmosphere, the alkaline-earthmetal compound or the zinc compound is reacted with a silicon compound,an aluminum compound, and a compound containing an element forming aluminescent center ion.

The production method 2 of the present invention is a method forproducing the above-mentioned a (M_(1-x)Lc_(x))₃N₂.bAlN.cSi₃N₄, inparticular, a M_(1-x)Lc_(x)AlSiN₃ phosphor, which may be called areducing and nitriding method, and in particular a production methodsuitable for industrial production of a powder-shaped phosphorcomposition.

Hereinafter, the production method 2 of the present invention will bedescribed in detail.

First, as a material for forming a phosphor host, a compound capable ofgenerating an oxide of the above-mentioned element “M” by heating, asilicon compound, and an aluminum compound are prepared. The compound(described later) capable of generating an oxide of the above-mentionedelement “M” by heating may be the one which is usually used as aceramics material. Such a material is easily obtained and inexpensive,and is stable in the atmosphere, so that it is easy to handle in theatmosphere.

Furthermore, as a material for adding a luminescent center ion, theabove-mentioned various kinds of rare-earth metals, transition metal, orcompounds thereof are prepared. In addition, as a reducing agent, carbonis prepared.

Next, these phosphor ingredients and the reducing agent are weighed andmixed so that the atomic ratio of the respective metal atoms becomes,for example, a (M_(1-x)Lc_(x))₃N₂.bAlN.cSi₃N₄, carbon monoxide gas (CO)is generated by the reaction with carbon (reducing agent), and oxygen inthe phosphor ingredient is removed completely, whereby a mixed materialis obtained. Herein, Lc represents a metal element to be a luminescentcenter ion, and “x” represents a numerical value satisfying 0<x<0.3,preferably 0.001≦x≦0.2, and more preferably 0.005≦x≦0.1.

Then, the mixed material is reacted by firing in a nitriding gasatmosphere. Herein, the nitriding gas refers to gas capable of effectinga nitriding reaction.

Furthermore, the preferable atmosphere for the purpose of generating alarge amount of ions such as Ce³⁺, Eu²⁺, Tb³⁺, or Mn²⁺, as a luminescentcenter ion, is a reducing atmosphere. The mixed material is fired, forexample, in a nitrogen-hydrogen mixed atmosphere. The firing temperatureis, for example, 1,300° C. to 2,000° C., and preferably 1,600° C. to2,000° C. and more preferably 1,700° C. to 1,900° C. for the purpose ofenhancing the performance of a phosphor. On the other hand, for thepurpose of mass-production, the firing temperature is preferably 1,400°C. to 1,800° C., more preferably 1,600° C. to 1,700° C. The firing timeis, for example, 30 minutes to 100 hours, preferably 2 to 8 hours inview of the productivity. Firing may be performed in differentatmospheres, or may be performed several times in the same atmosphere.The fired body obtained by such firing becomes a phosphor composition.

The compound capable of generating an oxide MO of the above-mentionedelement “M” by heating is not particularly limited. However, in terms ofthe ease of availability of a high-purity compound, the ease of handlingin the atmosphere, cost, and the like, the compound is preferably atleast one alkaline-earth metal compound or zinc compound selected fromthe group consisting of a carbonate, an oxalate, a nitrate, a sulfate,an acetate, an oxide, a peroxide, and a hydroxide of alkaline-earthmetal or zinc, more preferably a carbonate, an oxalate, an oxide, or ahydroxide of alkaline-earth metal, and most preferably a carbonate ofalkaline-earth metal.

There is no particular limit to the shape of the alkaline-earth metalcompound, and a powder shape, a lump shape, or the like may be selectedappropriately. The preferable shape for the purpose of obtaining apowder-shaped phosphor is powder.

There is no particular limit to the silicon compound as long as it iscapable of forming the phosphor composition of the present embodiment bythe above-mentioned reaction. The silicon compound is preferably siliconnitride (Si₃N₄) or silicon diimide (Si(NH)₂), more preferably siliconnitride for the same reason as that in the case of the alkaline-earthmetal compound or the reason that a phosphor with high performance canbe produced.

There is no particular limit to the shape of the silicon compound, and apowder shape, a lump shape, or the like can be selected appropriately.The preferable shape for the purpose of obtaining a powder-shapedphosphor is powder.

In the production method 2 of the present invention, a supply source ofsilicon may be elemental silicon. In this case, silicon is allowed toreact with nitrogen or the like in a nitriding gas atmosphere to form anitrogen compound of silicon (silicon nitride, etc.), and the nitrogencompound is allowed to react with the above-mentioned alkaline-earthmetal nitride, aluminum compound, and the like. For this reason,according to the production method 2 of the present invention, elementalsilicon also is included as the silicon compound.

There is no particular limit to the aluminum compound as long as it iscapable of forming the phosphor composition of the present embodiment bythe above-mentioned reaction. The aluminum compound is preferablyaluminum nitride (AlN) for the same reason as that in the case of theabove-mentioned silicon compound.

There is no particular limit to the shape of the aluminum compound, anda powder shape, a lump shape, or the like can be selected appropriately.The preferable shape of the aluminum compound for the purpose ofobtaining a powder-shaped phosphor is powder.

In the production method 2 of the present invention, a supply source ofaluminum may be elemental metal. In this case, aluminum is allowed toreact with nitrogen or the like in a nitriding gas atmosphere to form anitrogen compound of aluminum (aluminum nitride, etc.), and the nitrogencompound is allowed to react with the above-mentioned alkaline-earthmetal nitride, silicon compound, and the like. For this reason,according to the production method 2 of the present invention, metalaluminum is included as the aluminum compound.

There is no particular limit to the shape of the above-mentioned carbon.The preferable shape is solid-state carbon, and carbon black,high-purity carbon powder, carbon lump, or the like can be used. Amongthem, graphite is particularly preferable. However, amorphous carbon(coals, coke, charcoal, gas carbon, etc.) may be used. In addition, forexample, carbon hydride, such as natural gas, methane (CH₄), propane(C₃H₈), or propane (C₄H₁₀), which is carburizing gas, may be used as acarbon supply source. In the case of using a carbonaceous firingcontainer and heating element in a vacuum atmosphere or a neutralatmosphere such as an inactive gas atmosphere, a part of carbon may beevaporated. However, such evaporated carbon can be used as a reducingagent in principle.

There is no particular limit to the size and shape of theabove-mentioned solid-state carbon. For the reason of ease ofavailability, fine powder, powder, or particles with a longest diameteror longest side of 10 nm to 1 cm is preferable. Other solid-statecarbons may be used. Solid-state carbon in various shapes such as apowder shape, a particle shape, a lump shape, a plate shape, and a barshape can be used. The purity of the solid-state carbon is notparticularly limited, either. For the purpose of obtaining a nitridephosphor of high quality, the purity of the solid-state carbon ispreferably as high as possible. For example, it is preferable to usehigh-purity carbon with a purity of at least 99%, preferably at least99.9%.

The addition amount of the solid-state carbon is set to be a reactionratio stoichiometrically required for removing oxygen contained in thephosphor ingredient. Preferably, in order to remove the oxygencompletely, the addition amount of the solid-state carbon is set to be areaction ratio slightly larger than the stoichiometrically requiredreaction ratio. Regarding a specific numerical value, it is desirable toexcessively add the solid-state carbon in a range not exceeding 30atomic % of the stoichiometrically required reaction ratio.

The solid-state carbon to be reacted may be in a form that alsofunctions as a heating element (carbon heater) or also functions as afiring container (carbon crucible, etc.) The above carbon used as areducing agent may be mixed with a phosphor ingredient, or may be merelybrought into contact with the phosphor ingredient.

Furthermore, there is no particular limit to the nitriding gas, as longas it is capable of nitriding the above-mentioned alkaline-earth metalcompound or zinc compound reduced with carbon. In terms of the ease ofavailability, the ease of handling of high-purity gas, the cost, and thelike, at least one gas selected from nitrogen gas and ammonia gas, morepreferably nitrogen gas, is used. For the purpose of increasing thereducing power of a firing atmosphere and enhancing the performance of aphosphor, or obtaining a phosphor with high performance,nitrogen-hydrogen mixed gas also can be used.

As the reaction atmosphere containing nitriding gas, a normal-pressureatmosphere is preferable for the reason that a simple facility can beused. However, any of a high-pressure atmosphere, a compressedatmosphere, a reduced-pressure atmosphere, and a vacuum atmosphere maybe used. The preferable reaction atmosphere for the purpose of enhancingthe performance of a phosphor is a high-pressure atmosphere mainlycontaining nitrogen gas of, for example, 2 to 100 atm pressure,preferably 5 to 20 atm pressure in view of the handling of theatmosphere. With such a high-pressure atmosphere, the decomposition of anitride phosphor composition, which occurs during firing at hightemperature, can be prevented or suppressed, and the shift of thecomposition of a phosphor is suppressed, whereby a phosphor compositionwith high exhibition performance can be produced. For the purpose ofaccelerating the decarbonization of a reacted product (fired product), asmall or trace amount of water vapor may be contained in the abovereaction atmosphere.

Furthermore, in order to enhance the reactivity between theabove-mentioned compound materials, a flux may be added to be reacted.As the flux, an alkaline metal compound (Na₂CO₃, NaCl, LiF), or ahalogen compound (SrF₂, CaCl₂, etc.) can be selected appropriately.

The most significant features of the production method 2 of the presentinvention are as follows:

(1) As the material for the phosphor composition of the presentembodiment, a nitride of alkaline-earth metal or zinc, or alkaline-earthmetal or zinc metal is not substantially used;

(2) A compound is used instead, which is capable of generating a metaloxide (the above-mentioned MO) by heating;

(3) An oxygen component contained in these compounds is removed by thereaction with carbon, preferably solid-state carbon;

(4) The alkaline-earth metal compound is nitrided by the reaction withnitriding gas; and

(5) During the above reaction (4), a silicon compound is allowed toreact with an aluminum compound to produce the phosphor composition ofthe present embodiment.

In the production method 2 of the present invention, the preferablereaction temperature is 1,300° C. to 2,000° C., and the preferablereaction temperature for the purpose of enhancing the performance of aphosphor is 1,600° C. to 2,000° C. and more preferably 1,700° C. to1,900° C. On the other hand, for the purpose of mass-production, thepreferable reaction temperature is 1,400° C. to 1,800° C., morepreferably 1,600° C. to 1,700° C. The reaction also may be divided toseveral times. Thus, the compound capable of generating a metal oxide byheating becomes a metal oxide MO, and the metal oxide MO further isreacted with carbon to be reduced while generating carbon monoxide orcarbon dioxide. Furthermore, the reduced metal oxide is reacted withanother compound such as the silicon compound and aluminum compound, andgas while being nitrided with nitriding gas to form a nitride. Thus, thenitride phosphor composition of the present embodiment is generated.

At a temperature lower than the above-mentioned temperature range, theabove-mentioned reaction and reduction become insufficient, which makesit difficult to obtain a nitride phosphor composition of high quality.At a temperature higher than the above-mentioned temperature range, anitride phosphor composition is decomposed or fuses, which makes itdifficult to obtain a phosphor composition with a desired compositionand a desired shape (powder shape, molding shape, etc.). Furthermore, ata temperature higher than the above-mentioned temperature range, thereis no choice but to use an expensive heating element and a heatinsulating material with high insulation for production facility, whichincreases a facility cost, resulting in the difficulty in providing aphosphor composition at a low cost.

According to the production method 2 of the present invention, it is notnecessary to use a nitride of alkaline-earth metal or zinc, which isdifficult to obtain with high purity and difficult to handle in theatmosphere, as a main material for a phosphor. The production method 2of the present invention is characterized by allowing a materialcontaining a compound capable of generating an oxide of theabove-mentioned element “M” by heating, a silicon compound, an aluminumcompound, and carbon to react with a compound containing an elementforming a luminescent center ion in a nitriding gas atmosphere. Thesematerials are relatively inexpensive and easy to obtain, and are easy tohandle in the atmosphere. Therefore, these materials are suitable formass-production, and enable the phosphor of the present embodiment to beproduced at a low cost. Simultaneously, if the phosphor composition ofEmbodiment 1 produced by the production method 2 of the presentinvention is used, a light-emitting device can be provided at a lowercost.

As the supplemental description, the production method 2 of the presentinvention also is applicable to the production method 1 of the presentinvention described above. For example, when carbon as a reducing agentis added to at least one selected from a nitride (M₃N₂) ofalkaline-earth metal and a nitride (Zn₃N₂) of zinc, silicon nitride(Si₃N₄), and aluminum nitride (AlN), used as materials for forming aphosphor host, and the resultant mixture is fired, impurity oxygen canbe removed as carbon monoxide gas (CO) during firing, and oxygen can beprevented or suppressed from being mixed with a phosphor. Therefore, anitride phosphor composition with high purity can be produced.

More specifically, in a method for producing a nitride phosphorcomposition using at least one nitride selected from a nitride ofalkaline earth metal and a nitride of zinc as at least one of thephosphor ingredients, a method for producing a phosphor compositioncharacterized in that carbon is added to a phosphor ingredient to befired can be replaced with a method for producing a phosphor compositionof another embodiment. The above-mentioned nitride phosphor compositionrefers to a phosphor composition containing nitrogen as a gasifiableelement constituting a phosphor host, such as a nitride phosphorcomposition or an oxynitride phosphor composition, in particular, aphosphor composition containing nitrogen as a main gasifiable componentelement.

Even if some nitride compound such as Si₃N₄, M₂Si₅N₈, MSiN₂, or MSi₇N₁₀is mixed with a material for the phosphor composition containing acomposition represented by the above-mentioned MAlSiN₃ as a maincomponent of a phosphor host, followed by firing, a phosphor compositionexhibiting emission characteristics similar to those of theabove-mentioned phosphor composition is obtained. Thus, the phosphorcomposition of the present embodiment also may be a phosphor compositioncontaining, as a main component of a phosphor host, a nitriderepresented by any of a composition formula of MAlSiN₃.aSi₃N₄,MAlSiN₃.aM₂Si₅N₈, MAlSiN₃.aMSiN₂, and MAlSiN₃.aMSi₇N₁₀. Herein, “M” isat least one element selected from the group consisting of Mg, Ca, Sr,Ba, and Zn, and “a” is a numerical value satisfying 0≦a≦2, preferably0≦a≦1. Examples of such a phosphor composition include those in which aluminescent center ion is added to a composition such as 2MAlSiN₃.Si₃N₄,4MAlSiN₃.3Si₃N₄, MAlSiN₃.Si₃N₄, MAlSiN₃.2Si₃N₄, 2MAlSiN₃.M₂Si₅N₈,MAlSiN₃.M₂Si₅N₈, MAlSiN₃.2M₂Si₅N₈, 2MAlSiN₃.MSiN₂, MAlSiN₃.MAlSiN₂,MAlSiN₃.2MSiN₂, 2MAlSiN₃.MSi₇N₁₀, MAlSiN₃.MSi₇N₁₀, or MAlSiN₃.2MSi₇N₁₀.

Embodiment 2

Next, an embodiment of a light-limiting device of the present inventionwill be described. There is no particular limit to the embodiment of anexemplary light-emitting device of the present invention, as long as thephosphor composition of Embodiment 1 is used as a light-emitting source.For example, as an excitation source for a phosphor, at least oneelectromagnetic wave selected from an X-ray, an electron beam,ultraviolet light, near-ultraviolet light, visible light (light ofviolet, blue, green, or the like), near-infrared light, infrared light,and the like can be used. The phosphor of Embodiment 1 is allowed toemit light by applying an electric field or injecting an electronthereto, whereby the phosphor may be used as a light-emitting source.

Examples of the light-emitting device of the present embodiment includethose known by the following names: (1) fluorescent lamp, (2) plasmadisplay panel, (3) inorganic electroluminescence panel, (4) fieldemission display, (5) cathode-ray tube, and (6) white LED light source.

More specific examples of the light-emitting device of the presentembodiment include a white LED, various kinds of display devicesconfigured using a white LED (e.g., an LED information display terminal,an LED traffic light, an LED lamp for an automobile (a stop lamp, a turnsignal light, a headlight, etc.)), various kinds of illumination devicesconfigured using a white LED (an LED indoor-outdoor illumination lamp,an interior LED lamp, an LED emergency lamp, a LED light source, an LEDdecorative lamp), various kinds of display devices not using a white LED(a cathode-ray tube, an inorganic electroluminescence panel, a plasmadisplay panel, etc.), and various kinds of illumination devices (afluorescent lamp, etc.) not using a white LED.

In another aspect, the light-emitting device of the present embodimentis, for example, any of a white light-emitting element, various kinds oflight sources, an illumination device, a display device, and the like,obtained by combining an injection-type electroluminescence elementemitting near-ultraviolet light or blue light, (a light-emitting diode,a laser diode, an organic electroluminescence element, etc.) with atleast the phosphor composition of Embodiment 1. A display device, anillumination device, a light source, and the like configured using atleast one white light-emitting element also are included in theabove-mentioned light-emitting device.

The light-emitting device of the present embodiment is configured using,as a light-emitting source, a nitride phosphor composition emittinglight in a warm color having an emission peak in a wavelength range ofpreferably 580 nm to 660 nm, more preferably 610 nm to 650 nm, wherein,as the nitride phosphor composition, the phosphor composition ofEmbodiment 1 is used.

Furthermore, the light-emitting device of the present embodiment isconfigured, for example, by combining an emission source for emittingprimary light of 360 nm to less than 560 nm, and a phosphor compositionfor absorbing the primary light emitted by the emission source andconverting the primary light into visible light having a wavelengthlarger than that of the primary light, wherein, as the phosphorcomposition, the phosphor composition of Embodiment 1 (more preferably aphosphor composition emitting light in a warm color) is used. Morespecifically, the light-emitting device of the present embodiment isconfigured by combining an emission source for emitting light having anemission peak in any wavelength range of 360 nm to less than 420 nm, 420nm to less than 500 nm, and 500 nm to less than 560 nm, with a phosphorcomposition for absorbing primary light emitted by the emission sourceand converting the primary light into visible light having a wavelengthlarger than that of the primary light, wherein, as the phosphorcomposition, the phosphor composition of Embodiment 1 is used.

The light-emitting device of the present embodiment also can use aninjection-type electroluminescence element as the emission source. Theinjection-type electroluminescence element refers to a photoelectrictransducer configured so as to convert electric energy into light energyto obtain light emission by providing an electric power to inject acurrent to a fluorescent material. Specific examples thereof are asdescribed above.

The light-emitting device of the present embodiment is configured using,as a light-emitting source, a novel phosphor that is capable ofextending the range of choices of phosphor ingredients. Therefore, thelight-emitting device of the present embodiment can be configured at alow cost even without using a conventional expensive phosphor having ahigh scarcity value. Furthermore, the light-emitting device of thepresent embodiment is configured using, as a light-emitting source, aphosphor emitting light in a warm color, in particular, red light.Therefore, in the light-emitting device, the intensity of alight-emitting component in a warm color is high, and the special colorrendering index R9 has a large numerical value.

Hereinafter, the light-emitting device of the present embodiment will bedescribed with reference to the drawings. There is no particular limitto the light-emitting device of the present embodiment, as long as thephosphor composition of Embodiment 1 is used as a light-emitting source.Furthermore, in a preferable embodiment, the phosphor composition ofEmbodiment 1 and a light-emitting element are used as a light-emittingsource, and the phosphor composition is combined with the light-emittingelement so that the phosphor composition covers the light-emittingelement.

FIGS. 1, 2, and 3 are cross-sectional views of semiconductorlight-emitting devices that are typical embodiments of a light-emittingdevice including a combination of the phosphor composition of Embodiment1 and a light-emitting element.

FIG. 1 shows a semiconductor light-emitting device having aconfiguration in which at least one light-emitting element 1 is mountedon a submount element 4, and the light-emitting element 1 is sealed in apackage of a base material (e.g., transparent resin, low-melting glass)that also functions as a phosphor layer 3 containing at least thephosphor composition 2 of Embodiment 1. FIG. 2 shows a semiconductorlight-emitting device having a configuration in which at least onelight-emitting element 1 is mounted on a cup 6 provided at a mount leadof a lead frame 5, a phosphor layer 3 formed of a base materialcontaining at least the phosphor composition 2 of Embodiment 1 isprovided in the cup 6, and the entire body is sealed with a sealant 7made of resin or the like. FIG. 3 shows a semiconductor light-emittingdevice of a chip type having a configuration in which at least onelight-emitting element 1 is placed in a housing 8, and the phosphorlayer 3 formed of a base material containing at least the phosphorcomposition 2 of embodiment 1 is provided in the housing 8

In FIGS. 1 to 3, the light-emitting element 1 is a photoelectrictransducer that converts electric energy into light. Specific examplesof the light-emitting element 1 include a light-emitting diode, a laserdiode, a surface-emitting laser diode, an inorganic electroluminescenceelement, an organic electroluminescence element, and the like. Inparticular, the light-emitting diode or the surface-emitting laser diodeis preferable in terms of the high output of the semiconductorlight-emitting device. The wavelength of light emitted by thelight-emitting element 1 is not particularly limited, and may be in arange (e.g., 250 to 550 nm) capable of exciting the phosphor compositionof Embodiment 1. However, in order to produce a semiconductorlight-emitting device with high light-emitting performance, in which thephosphor composition of Embodiment 1 is excited at a high efficiency andwhich emits white light, the light-emitting element 1 is set so as tohave an emission peak in a wavelength range of more than 340 nm to 500nm, preferably more than 350 nm to 420 nm, or more than 420 nm to 500nm, more preferably more than 360 nm to 410 nm, or more than 440 nm to480 nm i.e., in a near-ultraviolet, violet, or blue wavelength range).

Furthermore, in FIGS. 1 to 3, the phosphor layer 3 contains at least thephosphor composition 2 of Embodiment 1. The phosphor layer 3 isconfigured, for example, by dispersing at least the phosphor composition2 of Embodiment 1 in a transparent base material such as transparentresin (epoxy resin, silicone resin, etc.), low-melting glass, or thelike. The content of the phosphor composition 2 in the transparent basematerial is preferably 5 to 80% by weight, more preferably 10 to 60% byweight, for example, in the case of the above-mentioned transparentresin. The phosphor composition 2 of Embodiment 1 present in thephosphor layer 3 is a light conversion material that absorbs a part oran entirety of light emitted from the light-emitting element 1 toconvert it into yellow to dark red light. Therefore, the phosphorcomposition 2 is excited by the light-emitting element 1, and thesemiconductor light-emitting device emits light containing at leastlight-emitting component light emitted by the phosphor composition 2.

Accordingly, with the light-emitting device described above having, forexample, the following combined configuration, white light is obtainedowing to the color mixture of light emitted by the light-emittingelement 1 and light emitted by the phosphor layer 3, and hence asemiconductor light-emitting element emitting white light, which ishighly demanded, can be obtained.

(1) A combined configuration of a light-emitting element emitting anylight of near-ultraviolet light (wavelength: 300 nm to less than 380 nm,preferably 350 nm to less than 380 nm in terms of the output) and violetlight (wavelength: 380 nm to less than 420 nm, preferably 395 nm to lessthan 415 nm in terms of the output), a blue phosphor, a green phosphor,and the red phosphor composition of Embodiment 1.

(2) A combined configuration of a light-emitting element emitting anylight of near-ultraviolet light and violet light, a blue phosphor, agreen phosphor, a yellow phosphor, and the red phosphor composition ofEmbodiment 1.

(3) A combined configuration of a light-emitting element emitting anylight of near-ultraviolet light and violet light, a blue phosphor, ayellow phosphor, and the red phosphor composition of Embodiment 1.

(4) A combined configuration of a light-emitting element emitting bluelight (wavelength: 420 nm to less than 490 nm, preferably 450 nm to lessthan 480 nm in terms of the output), a green phosphor, a yellowphosphor, and the red phosphor composition of Embodiment 1.

(5) A combined configuration of a light-emitting element emitting bluelight, a yellow phosphor, and the red phosphor composition of Embodiment1.

(6) A combined configuration of a light-emitting element emitting bluelight, a green phosphor, and the red phosphor composition of Embodiment1.

(7) A combined configuration of a light-emitting element emittingblue-green light (wavelength: 490 nm to less than 510 nm) and the redphosphor composition of Embodiment 1.

The phosphor composition of Embodiment 1 emitting red light can beexcited with green light with a wavelength of 510 nm to less than 560 nmor yellow light with a wavelength of 560 nm to less than 590 nm.Therefore, a semiconductor light-emitting device also can be producedthat has a configuration in which a light-emitting element emitting anyof the above-mentioned green light and yellow light is combined with thered phosphor composition of Embodiment 1.

Furthermore, since the phosphor composition of Embodiment 1 can emityellow light, the yellow phosphor composition of Embodiment 1 also canbe used as the yellow phosphor. Furthermore, in this case, a redphosphor other than the phosphor composition of Embodiment 1 may be usedas the red phosphor composition. Furthermore, even when a light-emittingelement emitting blue light is combined with the yellow phosphorcomposition of Embodiment 1, white light can be obtained.

The above-mentioned blue phosphor, green phosphor, yellow phosphor, andred phosphor other than the phosphor composition of Embodiment 1 can bewidely selected from an aluminate phosphor activated with Eu²⁺, ahalophosphate phosphor activated with Eu²⁺, a phosphate phosphoractivated with Eu²⁺, a silicate phosphor activated with Eu²⁺, a garnetphosphor activated with Ce³⁺ (n particular, YAG(yttrium-aluminum-garnet): Ce phosphor), a silicate phosphor activatedwith Tb³⁺, a thiogallate phosphor activated with Eu²⁺, a nitridephosphor activated with Eu²⁺ (in particular, a SIALON phosphor), analkaline-earth metal sulfide phosphor activated with Eu²⁺, an oxysulfidephosphor activated with Eu³⁺, and the like. More specifically, a (Ba,Sr)MgAl₁₀O₁₇:Eu²⁺ blue phosphor, a (Sr, Ca, Ba, Mg)₁₀(PO₄)₆Cl₂:Eu²⁺ bluephosphor, a (Ba, Sr)₂SiO₄:Eu²⁺ green phosphor, a BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺green phosphor, a Y₃(Al, Ga)₅O₁₂:Ce³⁺ green phosphor, a Y₃Al₅O₁₂:Ce³⁺green phosphor, a BaY₂SiAl₄O₁₂:Ce³⁺ green phosphor, a Ca₃Sc₂Si₃O₁₂:Ce³⁺green phosphor, a Y₂SiO₅:Ce³⁺, Tb³⁺ green phosphor, a BaSiN₂:Eu²⁺ greenphosphor, a SrGa₂S₄:Eu²⁺ green phosphor, a (Y, Gd)₃Al₅O₁₂:Ce³⁺ yellowphosphor, a Y₃Al₅O₁₂:Ce³⁺, Pr³⁺ yellow phosphor, a (Sr, Ba)₂SiO₄:Eu²⁺yellow phosphor, a CaGa₂S₄:Eu²⁺ yellow phosphor, a 0.75 CaO.2.25AlN.3.25 Si₃N₄:Eu²⁺ yellow phosphor, a CaS:Eu²⁺ red phosphor, a SrS:Eu²⁺red phosphor, a La₂O₂S:Eu³⁺ red phosphor, a Y₂O₂S:Eu³⁺ red phosphor, orthe like can be used.

Conventionally, a white LED with a high luminous flux and a high colorrendering property has been known, which uses a blue LED as anexcitation source of a phosphor, and contains, for example, anSr₂Si₅N₈:Eu²⁺ nitride red phosphor, and the above-mentioned YAG:Ceyellow phosphor or green phosphor in a phosphor layer. The phosphorcomposition of Embodiment 1 exhibits emission characteristics similar tothose of the above-mentioned Sr₂Si₅N₈:Eu²⁺ nitride red phosphor.Therefore, a light-emitting device, which uses a blue LED as anexcitation source of a phosphor, and includes a combination of the redphosphor composition of Embodiment 1 and the above-mentioned YAG:Cephosphor, also becomes a white LED emitting white light with a highluminous flux and a high color rendering property equal to those of theconventional light-emitting device.

The semiconductor light-emitting device in the present embodiment can beexcited with near-ultraviolet light to blue light, and is configuredusing the phosphor composition of Embodiment 1, which is easilyproduced, has a high emission intensity, is stable chemically, andcontains a large amount of red light-emitting component. Therefore, thesemiconductor light-emitting device in the present embodiment is alight-emitting device that has a higher emission intensity of a redlight-emitting component, is more excellent in reliability, and can beproduced at a lower cost, compared with the conventional light-emittingdevice.

Embodiment 3

FIGS. 4 and 5 respectively show a schematic view of a configuration ofan illumination•display device that is an example of the light-emittingdevice of the present invention. FIG. 4 shows an illumination•displaydevice configured using at least one semiconductor light-emitting device9 that is an example of the above-mentioned light-emitting device inwhich the phosphor composition of Embodiment 1 is combined with thelight-emitting element. FIG. 5 shows an illumination•display deviceincluding a combination of at least one light-emitting element 1 and thephosphor layer 3 containing at least the phosphor composition 2 ofEmbodiment 1. As the light-emitting element 1 and the phosphor layer 3,the ones similar to those of the semiconductor light-emitting device ofEmbodiment 2 can be used. Furthermore, the functions and effects of theillumination•display device with such a configuration also are similarto those of the semiconductor light-emitting device of Embodiment 2. InFIGS. 4 and 5, reference numeral 10 denotes output light.

FIGS. 6 to 12 respectively show a specific example of an illuminationdevice with the illumination•display device of the present embodimentincorporated thereto, schematically shown in FIGS. 4 and 5. FIG. 6 showsa perspective view of an illumination module 12 having an integratedlight-emitting portion 11. FIG. 7 shows a perspective view of theillumination module 12 having a plurality of light-emitting portions 11.FIG. 8 is a perspective view of a table lamp type illumination devicehaving the light-emitting portions 11 and being capable of controllingON-OFF and light amount with a switch 13. FIG. 9 is a side view of anillumination device as a light source configured using a screw cap 14, areflective plate 15, and an illumination module 12 having a plurality oflight-emitting portions 11. FIG. 10 is a bottom view of the illuminationdevice shown in FIG. 9. FIG. 11 is a perspective view of a plate typeimage display device provided with the light-emitting portions 11. FIG.12 is a perspective view a segmented number display device provided withthe light-emitting portions 11.

The illumination•display device in the present embodiment is configuredusing the phosphor composition of Embodiment 1 which is produced easily,has a high emission intensity, is chemically stable, and contains alarge amount of a red light-emitting component, or the semiconductorlight-emitting device of Embodiment 2 which has a high emissionintensity of a red light-emitting component, is excellent inreliability, and can be produced at a low cost. Therefore, theillumination•display device in the present embodiment has a higheremission intensity of a red light-emitting component, is more excellentin reliability, and can be produced at a lower cost, compared with theconventional illumination•display device.

Embodiment 4

FIG. 13 is a partially cut-away view of an end portion of a fluorescentlamp that is an exemplary light-emitting device using the phosphorcomposition of Embodiment 1. In FIG. 13, a glass tube 16 is sealed atboth end portions with stems 17, and noble gas such as neon, argon, orkrypton and mercury are sealed in the glass tube 16. The inner surfaceof the glass tube 16 is coated with the phosphor composition 18 ofEmbodiment 1. A filament electrode 20 is attached to the stem 17 withtwo leads 19. A cap 22 provided with an electrode terminal 21 isattached to the respective end portions of the glass tube 16, wherebythe electrode terminal 21 is connected to the leads 19.

There is no particular limit to the shape, size, and wattage of thefluorescent lamp of the present embodiment, and the color and colorrendering property of light emitted by the fluorescent lamp, and thelike. The shape of the fluorescent lamp of the present embodiment is notlimited to a straight tube as in the present embodiment. Examples of theshape of the fluorescent lamp include a round shape, a double annularshape, a twin shape, a compact shape, a U-shape, and a bulb shape, and anarrow tube for a liquid crystal backlight and the like also isincluded. Examples of the size include 4-type to 110-type. The wattagemay be selected appropriately in accordance with the application from arange of several watts to hundreds of watts. Examples of light colorinclude daylight color, neutral white color, white color, and warm whitecolor.

The fluorescent lamp in the present embodiment is configured using thephosphor composition of Embodiment 1 which is produced easily, has ahigh emission intensity, and contains a large amount of redlight-emitting component. Therefore, the fluorescent lamp in the presentembodiment has a higher emission intensity of a red light-emittingcomponent and can be produced at a lower cost, compared with theconventional fluorescent lamp.

Embodiment 5

FIG. 14 is a cross-sectional view of a double insulating configurationthin film electroluminescence panel, which is an exemplarylight-emitting device using the phosphor composition of Embodiment 1. InFIG. 14, a back substrate 23 holds a thin film EL panel, and formed ofmetal, glass, ceramics, or the like. A lower electrode 24 applies an ACvoltage of about 100 to 300 V to a laminated configuration of a thickfilm dielectric 25/thin film phosphor 26/thin film dielectric 27, and isa metal electrode or an In—Sn—O transparent electrode formed by aprocedure such as a printing technique. The thick film dielectric 25functions as film-formation substrate of the thin film phosphor 26, andalso limits the amount of charge flowing through the thin film phosphor26 during the application of the AC voltage. For example, the thick filmdielectric 25 is made of a ceramic material such as BaTiO₃ with athickness of 10 μm to several cm. Furthermore, the thin film phosphor 26is made of an electroluminescence material that emits fluorescence withhigh luminance when charge flows through the phosphor layer. The thinfilm phosphor 26 is, for example, a thioaluminate phosphor (bluelight-emitting BaAl₂S₄:Eu²⁺, blue light-emitting (Ba, Mg)Al₂S₄:Eu²⁺,etc.), a thiogallate phosphor (blue light-emitting CaGa₂S₄:Ce³⁺, etc.),or the like formed into a film by a thin film technique such as anelectron beam vapor evaporation, or sputtering. The thin film dielectric27 limits the amount of charge flowing through the thin film phosphor26, and prevents the thin film phosphor 26 from reacting with watervapor in the atmosphere to be degraded. The thin film dielectric 27 is,for example, a translucent dielectric such as silicon oxide or aluminumoxide, formed into a film by a thin film technique such as chemicalvapor deposition or sputtering. An upper electrode 28 is paired with thelower electrode 24, and applies an AC voltage of about 100 to 300 V tothe laminated configuration of the thick film dielectric 25/thin filmphosphor 26/thin film dielectric 27. The upper electrode 28 is, forexample, a transparent electrode made of In—Sn—O or the like formed onthe upper surface of the thin film dielectric 27 by a thin filmtechnique such as vacuum deposition or sputtering. Alight wavelengthconverting layer 29 converts light (e.g., blue light) emitted by thethin film phosphor 26 and passing through the thin film dielectric 27and the upper electrode 28 into, for example, green light, yellow light,or red light. The light wavelength converting layer 29 also can beprovided in a plurality of kinds. A surface glass 30 protects the doubleinsulating configuration thin film EL panel thus configured.

When an AC voltage of about 100 to 300 V is applied between the lowerelectrode 24 and the upper electrode 28 of the thin film EL panel, avoltage of about 100 to 300 V is applied to a laminated configuration ofthe thick film dielectric 25/thin film phosphor 26/thin film dielectric27, and charge flows through the thin film phosphor 26, whereby the thinfilm phosphor 26 emits light. This emitted light excites the lightwavelength converting layer 29 through the thin film dielectric 27 andthe upper electrode 28 having translucency to have its wavelengthconverted. The light with its wavelength converted passes through thesurface glass 30 and is output from the panel to be observed fromoutside of the panel.

In the embodiment of the light-emitting device using the phosphorcomposition of Embodiment 1, at least one light wavelength convertinglayer 29 is configured using the phosphor composition of Embodiment 1,in particular, the phosphor composition emitting red light. Furthermore,in a preferred embodiment, the thin film phosphor 26 is set to be a thinfilm blue phosphor emitting blue light, and the light wavelengthconverting layer 29 is composed of a wavelength converting layer 31 forconverting light into green light, made of a blue excitation greenlight-emitting material (e.g., a SrGa₂S₄:Eu²⁺ phosphor), and awavelength converting layer 32 having the phosphor composition ofEmbodiment 1 emitting red light, which functions as a wavelengthconverting layer for converting light into red light. Furthermore, asshown in FIG. 14, a part of blue light emitted by the thin film bluephosphor is output from the panel without exciting the light wavelengthconverting layer 29. Furthermore, the electrode configuration is set tobe a lattice shape that can be driven in a matrix.

When the light-emitting device is designed so as to emit blue light 33emitted by the thin film phosphor 26, green light 34 with its wavelengthconverted by the light wavelength converting layer 29 (31), and redlight 35 with its wavelength converted by the light wavelengthconverting layer 29 (32), the light-emitting device emits light of threeprimary colors (blue, green, and red). Furthermore, the lighting ofrespective pixels emitting light of blue, green, and red can becontrolled independently, so that a display device capable of performinga full-color display can be provided.

In a preferred embodiment of the light-emitting device using thephosphor composition of Embodiment 1, a part of the light wavelengthconverting layer 29 is configured using the red phosphor composition ofEmbodiment 1 that is produced easily and stable chemically, and isexcited with blue light to emit red light having satisfactory colorpurity. Thus, a highly reliable light-emitting device having red pixelsexhibiting satisfactory red emission characteristics can be provided.

As described above, the present invention can provide a novel phosphorcomposition capable of emitting light in a warm color (in particular,red light), containing as a main component of a phosphor host, theabove-mentioned composition represented by a composition formula:aM₃N₂.bAlN.cSi₃N₄. The present invention also can provide a method forproducing a nitride phosphor composition of the present invention, whichis suitable for mass-production and can be produced at a low cost.Furthermore, according to the present invention, by using a novelnitride phosphor composition with a high efficiency, a light-emittingdevice also can be provided, which has a high emission intensity of alight-emitting component in a warm color (in particular, red) and isinexpensive, and is novel in terms of the configuration of materials tobe used.

Hereinafter, the present invention will be described specifically by wayof examples.

Example 1

As the nitride phosphor composition of the present invention, a phosphorcomposition substantially represented by Sr_(0.98)Eu_(0.02)AlSiN₃ wasproduced as follows.

In the present example, the following compounds were used as phosphoringredients.

(1) Strontium nitride powder (Sr₃N₂: purity 99.5%): 25.00 g

(2) Europium oxide powder (Eu₂O₃: purity 99.9%): 0.93 g

(3) Silicon nitride powder (Si₃N₄: purity 99%): 13.00 g

(4) Aluminum nitride powder (AlN: purity 99.9%): 10.78 g

These phosphor ingredients were weighed in a nitrogen atmosphere using aglove box, and then mixed thoroughly with a mortar. Thereafter, themixed powder was placed in an alumina crucible. The alumina crucible wasplaced at a predetermined position in an atmospheric furnace, and heatedin nitrogen-hydrogen mixed gas (97% nitrogen and 3% hydrogen) at 1600°C. for 2 hours. For simplicity, the aftertreatments such as pulverizing,classification, and washing are omitted.

Hereinafter, the characteristics of the fired product (SrASiN₃:Eu²⁺phosphor composition) obtained by the above-mentioned production methodwill be described.

The body color of the above-mentioned phosphor composition was vibrantorange. FIG. 15 shows an emission spectrum (254 nm excitation) 37 and anexcitation spectrum 36 of the phosphor composition of the presentexample obtained by the above-mentioned production method. FIG. 15 showsthat the above-mentioned fired product is a red phosphor having anemission peak in the vicinity of a wavelength of 635 nm, which isexcited with light in a large wavelength range of 220 nm to 600 nm(i.e., ultraviolet light-near-ultraviolet light-violet light-bluelight-green light-yellow light-orange light). The chromaticity (x, y) ofemitted light in a CIE chromaticity coordinate was x=0.612 and y=0.379.

Constituent metal elements of the above-mentioned fired product wereevaluated by semiquantitative analysis using a fluorescent X-rayanalysis method. Consequently, the fired product was found to be acompound mainly containing Sr, Eu, Al, and Si.

These results suggest that a composition represented by(Sr_(0.98)Eu_(0.02))AlSiN₃ was produced and an SrAlSiN₃:Eu²⁺ phosphorwas produced by the production method of the present example.

For reference, FIG. 16 shows an X-ray diffraction pattern of thephosphor composition of the present example. As shown in FIG. 16, it isunderstood that the phosphor composition of the present example is atleast a crystalline phosphor in which a plurality of strong diffractionpeaks, different from the diffraction peak of a phosphor ingredient suchas an alkaline-earth metal oxide, silicon nitride, or aluminum nitride,or the diffraction peak of a conventionally known Sr₂Si₅N₈ compound, arerecognized in the vicinity of a diffraction angle (2θ) of 28° to 37° inthe diffraction pattern evaluation by the X-ray diffraction method undernormal pressure and temperature using a Cu-Kα ray.

In the present example, it is considered based on the following ChemicalReaction Formula 1 that a compound represented by a chemical formula:(Sr_(0.98)Eu_(0.02))AlSiN₃, or a composition represented by acomposition formula: (Sr_(0.98)Eu_(0.02))AlSiN₃ or a composition formulaclose thereto was generated.1.96Sr₃N₂+0.06Eu₂O₃+2Si₃N₄+6AlN+0.04N₂+0.18H₂→6Sr_(0.98)Eu_(0.02)AlSiN₃+0.18H₂O↑  (ChemicalReaction Formula 1)

Thus, according to the production method of the present invention,although Sr₃N₂ that is unstable chemically, difficult to handle in theatmosphere, and expensive was used, a SrAlSiN₃:Eu²⁺ phosphor wasproduced.

In the present example, the case of the nitride phosphor compositioncontaining Eu²⁺ ions as a luminescent center ion has been described. Aphosphor composition containing a luminescent center ion (e.g., Ce³⁺ions) other than Eu²⁺ ions also can be produced by the same productionmethod.

Example 2

As the nitride phosphor composition of the present invention, a phosphorcomposition substantially represented by Sr_(0.98)Eu_(0.02)AlSiN₃ wasproduced by a production method different from that of Example 1 asfollows.

In the present example, the following compounds were used as phosphoringredients.

(1) Strontium carbonate powder (SrCO₃: purity 99.9%): 2.894 g

(2) Europium oxide powder (Eu₂O₃: purity 99.9%): 0.070 g

(3) Silicon nitride powder (Si₃N₄: purity 99%): 0.988 g

(4) Aluminum nitride powder (AlN: purity 99.9%): 0.820 g

Furthermore, as the reducing agent (added reducing agent) of theabove-mentioned strontium carbonate and europium oxide, the followingsolid-state carbon was used.

(5) Carbon (graphite) powder (C: purity 99.9%): 0.240 g

First, these phosphor ingredients and the added reducing agent weremixed thoroughly with an automatic mortar. Thereafter, the mixed powderwas placed in an alumina crucible. The alumina crucible was placed at apredetermined position in an atmospheric furnace, and heated innitrogen-hydrogen mixed gas (97% nitrogen and 3% hydrogen) at 1600° C.for 2 hours. For simplicity, the aftertreatments such as pulverizing,classification, and washing are omitted.

Hereinafter, the characteristics of the fired product (SrAlSiN₃:Eu²⁺phosphor composition) obtained by the above-mentioned production methodwill be described.

The body color of the above-mentioned phosphor composition was orange.FIG. 17 shows an emission spectrum (254 nm excitation) 37 and anexcitation spectrum 36 of the phosphor composition of the presentexample obtained by the above-mentioned production method. FIG. 17 showsthat the above-mentioned fired product is a red phosphor having anemission peak in the vicinity of a wavelength of 640 nm, which isexcited with light in a large wavelength range of 220 nm to 600 nm(i.e., ultraviolet light-near-ultraviolet light-violet light-bluelight-green light-yellow light-orange light.

Constituent metal elements of the above-mentioned fired product wereevaluated by semiquantitative analysis using a fluorescent X-rayanalysis method. Consequently, the fired product was found to be acompound mainly containing Sr, Eu, Al, and Si.

These results suggest that a composition represented by(Sr_(0.98)Eu_(0.02))AlSiN₃ was produced and an SrAlSiNa:Eu²⁺ phosphorwas produced by the production method of the present example.

For reference, FIG. 18 shows an X-ray diffraction pattern of thephosphor composition of the present example. As shown in FIG. 18, it isunderstood that the phosphor composition of the present example is atleast a crystalline phosphor in which a plurality of strong diffractionpeaks, different from the diffreaction peak of a phosphor ingredientsuch as an alkaline-earth metal oxide, silicon nitride, or aluminumnitride, or the diffraction peak of a conventionally known Sr₂Si₅N₈compound, are recognized in the vicinity of a diffraction angle (2θ) of30° to 37° in the diffraction pattern evaluation by the X-raydiffraction method under normal pressure and temperature using a Cu-Kαray.

In the present example, it is considered based on the following ChemicalReaction Formula 2 that SrO of an alkaline-earth metal oxide was reactedwith nitrogen and silicon nitride while being substantially reduced bycarbon together with EuO as a lanthanide oxide, whereby a compoundrepresented by a chemical formula: (Sr_(0.98)Eu_(0.02))AlSiN₃, or acomposition represented by a composition formula:(Sr_(0.98)Eu_(0.02))AlSiN₃ or a composition formula close thereto wasgenerated.0.98SrCO₃+0.01Eu₂O₃+(⅓)Si₃N₄+AlN+C+(⅓)N₂+0.01H₂→Sr_(0.98)Eu_(0.02)AlSiN₃+0.98CO₂↑+CO↑+0.01H₂O↑  (Chemical Reaction Formula 2)

Thus, according to the production method of the present invention, aSrAlSiN₃:Eu²⁺ phosphor was produced using strontium carbonate that iseasy to handle and inexpensive as a supply source of alkaline-earthmetal, without using Sr metal or Sr₃N₂ that is unstable chemically,difficult to handle in the atmosphere, and expensive.

Hereinafter, the characteristics of the SrAlSiN₃:Eu²⁺ phosphorcomposition of Example 2 will be described in the case where thereplacement ratio of Eu (=Eu replacement amount: Eu/(Sr+Eu)×100 (atomic%)) with respect to Sr is varied.

FIG. 19 shows emission spectra of the SrAlSiN₃:Eu²⁺ phosphorcompositions having different Eu replacement amounts under theexcitation with a UV-ray of 254 nm. As is understood from FIG. 19, theemission peak wavelength shifted gradually from about 615 nm (Eureplacement amount: 0.1 to 0.3 atomic %) to a long wavelength side, andvaried within a range up to about 750 nm (Eu replacement amount: 100atomic %), as the Eu replacement amount increased. Furthermore, as theEu replacement amount increased, the emission peak intensity increasedgradually, and decreased gradually after the Eu replacement amountexhibited a maximum value in the vicinity of 1 to 3 atomic %. Even whenthe composition was excited with ultraviolet light-near-ultravioletlight-violet light-blue light-green light in a wavelength range of 250nm to 550 nm, there was hardly any change in a peak position of anemission spectrum.

FIG. 20 shows a summary of the relationship between the Eu replacementamount of the SrAlSiN₃:Eu²⁺ phosphor composition with respect to analkaline-earth metal element (Sr) and the emission peak wavelengththereof. Considering that the emission peak wavelength suitable for alight-emitting device is 610 nm to 660 nm, preferably 620 nm to 650 nm,it is understood from FIG. 20 that the Eu replacement amount preferableas a red phosphor for a light-emitting device is 0.1 atomic % to lessthan 7 atomic %:

Furthermore, FIG. 21 shows a summary of the relationship between the Eureplacement amount of the SrAlSiN₃:Eu²⁺ phosphor composition withrespect to an alkaline-earth metal element (Sr) and the emission peakheight (emission intensity). Even in the case where the peak wavelengthof an excitation light source is varied in a wavelength range of 250 nmto 550 nm, the same tendency is recognized. It is understood from FIG.21 that the Eu replacement amount preferable in terms of the emissionintensity is 0.3 atomic % to less than 6 atomic %, preferably 1 atomic %to less than 4 atomic %.

More specifically, it is understood from FIGS. 20 and 21 that the Eureplacement amount preferable as a red phosphor for a light-emittingdevice is 0.1 atomic % to 7 atomic %, preferably 1 atomic % to less than4 atomic %.

In the present example, the case of the nitride phosphor compositioncontaining Eu²⁺ ions as a luminescent center ion has been described. Aphosphor composition containing a luminescent center ion other than Eu²⁺ions also can be produced by the same production method.

Example 3

As the nitride phosphor composition of the present invention, a phosphorcomposition substantially represented by Sr_(0.98)Ce_(0.02)AlSiN₃ wasproduced as follows.

In the present example, the following compounds were used as phosphoringredients.

(1) Strontium carbonate powder (SrCO₃: purity 99.9%): 2.894 g

(2) Cerium oxide powder (CeO₂: purity 99.99%): 0.069 g

(3) Silicon nitride powder (Si₃N₄: purity 99%): 0.988 g

(4) Aluminum nitride powder (AlN: purity 99.9%): 0.820 g

Furthermore, as the reducing agent of the above-mentioned strontiumcarbonate and cerium oxide, the following solid-state carbon was used.

(5) Carbon (graphite) powder (C: purity 99.9%): 0.240 g

Using these phosphor ingredients, a phosphor composition was produced bythe same procedure/condition as that of Example 2.

Hereinafter, the characteristics of the fired product (SrAlSiN₃:Ce³⁺phosphor composition) obtained by the above-mentioned production methodwill be described.

The body color of the above-mentioned phosphor composition was whitetaking on blue-green. FIG. 22 shows an emission spectrum (254 nmexcitation) 37 and an excitation spectrum 36 of the phosphor compositionof the present example obtained by the above-mentioned productionmethod. FIG. 22 shows that the above-mentioned fired product is ablue-green phosphor having an emission peak in the vicinity of awavelength of 504 nm, which is excited with light in a large wavelengthrange of 220 nm to 450 nm (i.e., ultraviolet light-near-ultravioletlight-violet light-blue light).

These results suggest that a composition represented by SrAlSiN₃:Ce³⁺was produced by the production method of the present example.

Even in the present example, it is considered based on the same ChemicalReaction Formula as that of Example 2 that SrO of an alkaline-earthmetal oxide was reacted with nitrogen and silicon nitride while beingsubstantially reduced by carbon together with CeO₂ as a lanthanideoxide, whereby a composition represented by a composition formula closeto (Sr_(0.98)Ce_(0.02))AlSiN₃ was generated.

Thus, according to the production method of the present example, aSrAlSiN₃:Ce³⁺ phosphor was produced using strontium carbonate that iseasy to handle and inexpensive as a supply source of alkaline-earthmetal, without using Sr metal or Sr₃N₂ that is unstable chemically,difficult to handle in the atmosphere, and expensive.

Example 4

As the nitride phosphor composition of the present invention, a phosphorcomposition substantially represented by Ca_(0.98)Eu_(0.02)AlSiN₃ wasproduced as follows.

In the present example, a phosphor composition was produced by the sameproduction method and under the same firing condition as those ofExample 2, except for using the following materials as phosphoringredients and an added reducing agent (carbon powder).

(1) Calcium carbonate powder (CaCO₃: purity 99.9%): 1.962 g

(2) Europium oxide powder (Eu₂O₃: purity 99.9%): 0.070 g

(3) Silicon nitride powder (Si₃N₄: purity 99%): 0.988 g

(4) Aluminum nitride powder (AlN: purity 99.9%): 0.820 g

(5) Carbon (graphite) powder (C: purity 99.9%): 0.240 g

Hereinafter, the characteristics of the fired product (CaAlSiN₃:Eu²⁺phosphor composition) obtained by the above-mentioned production methodwill be described.

The body color of the above-mentioned phosphor was orange. FIG. 23 showsan emission spectrum (254 nm excitation) 37 and an excitation spectrum36 of the phosphor composition of the present example obtained by theabove-mentioned production method. FIG. 23 shows that theabove-mentioned fired product is a red-orange phosphor having anemission peak in the vicinity of a wavelength of 600 nm, which isexcited with light in a large wavelength range of 220 nm to 550 nm(i.e., ultraviolet light-near-ultraviolet light-violet light-bluelight-green light). The chromaticity (x, y) of emitted light in a CIEchromaticity coordinate was x=0.496 and y=0.471.

Constituent metal elements of the above-mentioned fired product wereevaluated by semiquantitative analysis using a fluorescent X-rayanalysis method. Consequently, the fired product was found to be acompound mainly containing Ca, Eu, Al, and Si.

These results suggest that a composition represented by(Ca_(0.98)Eu_(0.02))AlSiN₃ was produced and a CaASiN₃:Eu²⁺ phosphor wasproduced by the production method of the present example.

In the present example, it is considered based on the following ChemicalReaction Formula 3 that CaO of an alkaline-earth metal oxide was reactedwith nitrogen and silicon nitride while being substantially reduced bycarbon together with EuO as a lanthanide oxide, whereby a compoundrepresented by a chemical formula: (Ca_(0.98)Eu_(0.02))AlSiN₃, or acomposition represented by a composition formula:(Ca_(0.98)Eu_(0.02))AlSiN₃ or a composition formula close thereto wasgenerated.0.98 CaCO₃+0.01Eu₂O₃+(⅓)Si₃N₄+AlN+C+(⅓)N₂+0.01H₂→Ca_(0.98)Eu_(0.02)AlSiN₃+0.98CO₂↑+CO↑+0.01H₂O↑  (Chemical Reaction Formula 3)

Thus, according to the production method of the present example, aCaAlSiNs:Eu²⁺ phosphor was produced using calcium carbonate that is easyto handle and inexpensive as a supply source of alkaline-earth metal,without using Ca metal or Ca₃N₂ that is unstable chemically, difficultto handle in the atmosphere, and expensive.

In the present example, the case of the nitride phosphor compositioncontaining Eu²⁺ ions as a luminescent center ion has been described. Aphosphor composition containing a luminescent center ion (e.g., Ce³⁺ions) other than Eu²⁺ ions also can be produced by the same productionmethod.

Furthermore, in the present example, the case of the production methodusing carbon powder as an added reducing agent has been described. ACaAlSiN₃:Eu²⁺ phosphor can be produced similarly even by the sameproduction method as that of Example 1, using, as phosphor ingredients,for example, a nitride of an alkaline-earth metal element, calcium,(Ca₃N₂), silicon nitride (Si₃N₄), aluminum nitride (AlN), and an Eumaterial (europium oxide (Eu₂O₃), europium nitride (EuN), metal Eu,etc.) without using an added reducing agent.

By appropriately selecting the addition amount of Eu²⁺ and productioncondition, red light having an emission peak in a wavelength range of610 nm to less than 650 nm also can be obtained from the CaAlSiN₃:Eu²⁺phosphor. The CaAlSiN₃:Eu²⁺ phosphor may be a red phosphor.

Examples 5 to 8

Hereinafter, as the phosphor compositions of Examples 5 to 8 accordingto the present invention, phosphor compositions each containing, as amain component of a phosphor host, a nitride substantially representedby SrAlSiN₃.a′Si₃N₄ were produced as follows.

As an example, a method for producing phosphor compositions with 2atomic % of Sr replaced by Eu, respectively containing, as a phosphorhost, compositions with the numerical value of a′ being 0.5, 0.75, 1,and 2 (i.e., 2 SrAlSiN₃.Si₃N₄, 4SrAlSiN₃.3Si₃N₄, SrAlSiN₃.Si₃N₄, andSrAlSiN₃.2Si₃N₄), and the characteristics thereof will be described.

In the production of the above-mentioned compositions, the same phosphoringredients and added reducing agent as those described in Example 2have been used. The phosphor compositions were produced and evaluated bythe same procedure and under the same condition as those in Example 2,except that the mixed ratios were set to be the weight ratios shown inTable 1.

TABLE 1 Composition formula SrCO₃ Eu₂O₃ Si₃N₄ AlN C Example 52(Sr_(0.98)Eu_(0.02))AlSiN₃•Si₃N₄ 5.787 g 0.141 g 4.942 g 1.639 g 0.480g Example 6 4(Sr_(0.98)Eu_(0.02))AlSiN₃•3Si₃N₄ 11.574 g  0.282 g 12.849g  3.279 g 0.961 g Example 7 (Sr_(0.98)Eu_(0.02))AlSiN₃•Si₃N₄ 2.894 g0.070 g 3.953 g 0.820 g 0.240 g Example 8(Sr_(0.98)Eu_(0.02))AlSiN₃•2Si₃N₄ 2.894 g 0.070 g 6.919 g 0.820 g 0.240g

Hereinafter, the characteristics of the phosphor compositions thusobtained will be described.

The body colors of the phosphor compositions were all orange. As arepresentative example, FIGS. 24 to 27 show an emission spectrum (254 nmexcitation) 37 and an excitation spectrum 36 of the phosphorcompositions of Examples 5 to 8 obtained by the above-mentionedproduction method. FIGS. 24 to 27 show that the above-mentioned firedproducts are all red phosphors having an emission peak in the vicinityof a wavelength of 640 nm, which are excited with light in a largewavelength range of 220 nm to 600 nm (i.e., ultravioletlight-near-ultraviolet light-violet light-blue light-green light-yellowlight-orange light).

Although detailed data is omitted, even in the phosphor composition inwhich Eu²⁺ ions were added to the composition with Sr₂Si₅N₈, SrSiN², andSrSi₇N₁₀ excessively added to the above-mentioned SrAlSiN₃ (i.e., thenitride phosphor composition with Eu²⁺ ions added thereto as an exampleof a luminescent center, containing, as a phosphor host, a compositionsubstantially represented by SrAlSiN₃.a′Sr₂Si₅N₈, SrAlSiN₃.a′SrSiN², orthe like), as well as the phosphor composition in which Eu²⁺ ions wereadded to the composition with Si₃N₄ added excessively to SrAlSiN₃ asdescribed in Examples 5 to 8, the same emission characteristics as thoseof the above-mentioned phosphor composition in which Eu²⁺ ions wereadded to a composition with Si₃N₄ excessively added thereto, wererecognized. The above-mentioned a′ is a numerical value satisfying0≦a′≦2, preferably 0≦a′≦1, specifically, a numerical value such as 0,0.25, 0.33, 0.5, 0.67, 0.75, 1, 1.5, or 2. Therefore, a′ also can be setto be a numerical value satisfying 0.25≦a′≦2, preferably 0.25≦a′≦1.

It has not been confirmed whether excess Si₃N₄, Sr₂Si₅N₈, SrSiN², andSrSi₇N₁₀ are present in these phosphor compositions together with theabove-mentioned SrAlSiN₃, or contribute to the formation of novelcompounds such as Sr₂Al₂Si₅N₀₁, Sr₄Al₄Si₁₃N₂₄, SrAlSi₄N₇, SrAlSi₇N₁₁,Sr₄Al₂Si₇N₁₄, Sr₃AlSi₆N₁₁, Sr₅AlSi₁₁N₁₁, Sr₃Al₂Si₃N₈, Sr₂AlSi₂N₅,Sr₃AlSi₃N₇, Sr₃Al₂Si₉N₁₆, Sr₂AlSi₈N₁₃, and Sr₃AlSi₁₅N₂₃ to allow thesenovel compounds to function as a phosphor host. It is necessary toinvestigate using various kinds of crystal structure analysisprocedures, and both cases may be possible.

Examples 9 to 25

As the phosphor compositions of Examples 9 to 25 of the presentinvention, phosphor compositions containing, as a main component of aphosphor host, a composition substantially represented byaSr₃N₂.bAlN.cSi₃N₄ were produced as follows.

As an example, Tables 2, 3, and 6 show phosphor compositions with 2atomic % of Sr replaced by Eu with the numerical values of “a”, “b”, and“c” being those shown in Table 2, and the production method andcharacteristics thereof will be described. Although the phosphorcompositions in Tables 2, 3, and 6 may be represented differently, theyhave the same composition ratios, respectively.

TABLE 2 a b C Phosphor composition Example 9 2 3 22(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•2Si₃N₄ Example 10 1 1 1(Sr_(0.98)Eu_(0.02))₃N₂•AlN•Si₃N₄ Example 11 4 3 44(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•4Si₃N₄ Example 12 1 2 1(Sr_(0.98)Eu_(0.02))₃N₂•2AlN•Si₃N₄ Example 13 1 1 2(Sr_(0.98)Eu_(0.02))₃N₂•AlN•2Si₃N₄ Example 14 5 3 115(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•11Si₃N₄ Example 15 7 3 167(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•16Si₃N₄ Example 16 4 6 74(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•7Si₃N₄ Example 17 2 3 82(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•8Si₃N₄ Example 18 1 1 5(Sr_(0.98)Eu_(0.02))₃N₂•AlN•5Si₃N₄ Example 19 4 3 224(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•22Si₃N₄ Example 20 1 2 3(Sr_(0.98)Eu_(0.02))₃N₂•2AlN•3Si₃N₄ Example 21 1 3 10(Sr_(0.98)Eu_(0.02))₃N₂•3AlN•10Si₃N₄ Example 22 1 2 3(Sr_(0.98)Eu_(0.02))₃N₂•2AlN•3Si₃N₄ Example 23 5 6 145(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•14Si₃N₄ Example 24 7 6 197(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•19Si₃N₄ Example 25 9 6 249(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•24Si₃N₄

TABLE 3 Phosphor composition Example 9(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))SiN₂ Example 10(Sr_(0.98)Eu_(0.02))AlSiN₃•2(Sr_(0.98)Eu_(0.02))SiN₂ Example 11(Sr_(0.98)Eu_(0.02))AlSiN₃•3(Sr_(0.98)Eu_(0.02))SiN₂ Example 122(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))SiN₂ Example 13(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))₂Si₅N₈ Example 14(Sr_(0.98)Eu_(0.02))AlSiN₃•2(Sr_(0.98)Eu_(0.02))₂Si₅N₈ Example 15(Sr_(0.98)Eu_(0.02))AlSiN₃•3(Sr_(0.98)Eu_(0.02))₂Si₅N₈ Example 162(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))₂Si₅N₈ Example 17(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))Si₇N₁₀ Example 18(Sr_(0.98)Eu_(0.02))AlSiN₃•2(Sr_(0.98)Eu_(0.02))Si₇N₁₀ Example 19(Sr_(0.98)Eu_(0.02))AlSiN₃•3(Sr_(0.98)Eu_(0.02))Si₇N₁₀ Example 202(Sr_(0.98)Eu_(0.02))AlSiN₃•(Sr_(0.98)Eu_(0.02))Si₇N₁₀ Example 21(Sr_(0.98)Eu_(0.02))AlSiN₃•3Si₃N₄ Example 22(Sr_(0.98)Eu_(0.02))₃Al₂Si₉N₁₆ Example 23(Sr_(0.98)Eu_(0.02))₅Al₂Si₁₄N₂₄ Example 24(Sr_(0.98)Eu_(0.02))₇Al₂Si₁₉N₃₂ Example 25(Sr_(0.98)Eu_(0.02))₉Al₂Si₂₄N₄₀

As Comparative Examples 1 to 5, Tables 4, 5, and 6 show phosphorcompositions with 2 atomic % of Sr replaced by Eu, with the numericalvalues of “a”, “b”, and “c” being those shown in Table 4, and thesecompositions were produced and evaluated in the same way as the above.Although the phosphor compositions in Tables 4, 5, and 6 may berepresented differently, they have the same composition ratios,respectively.

TABLE 4 a b c Phosphor composition Comparative 1 6 1(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•Si₃N₄ Example 1 Comparative 1 9 1(Sr_(0.98)Eu_(0.02))₃N₂•9AlN•Si₃N₄ Example 2 Comparative 2 9 22(Sr_(0.98)Eu_(0.02))₃N₂•9AlN•2Si₃N₄ Example 3 Comparative 1 6 4(Sr_(0.98)Eu_(0.02))₃N₂•6AlN•4Si₃N₄ Example 4 Comparative 2 0 52(Sr_(0.98)Eu_(0.02))₃N₂•5Si₃N₄ Example 5

TABLE 5 Phosphor composition Comparative (Sr_(0.98)Eu_(0.02))AlSiN₃•AlNExample 1 Comparative (Sr_(0.98)Eu_(0.02))AlSiN₃•2AlN Example 2Comparative 2(Sr_(0.98)Eu_(0.02))AlSiN₃•AlN Example 3 Comparative(Sr_(0.98)Eu_(0.02))Al₂Si₄N₈ Example 4 Comparative(Sr_(0.98)Eu_(0.02))₂Si₅N₈ Example 5

In the production of these compositions, the same phosphor ingredientsand added reducing agent as those described in Example 2 were used.Phosphor compositions were produced and evaluated by the same procedureand under the same condition as those in Example 2, except that themixed weight ratios were set to be the weight ratios shown in Table 6.

TABLE 6 Composition formula SrCO₃ Eu₂O₃ Si₃N₄ AlN C Example 9(Sr_(0.98)Eu_(0.02))₂AlSi₂N₅ 5.787 g 0.141 g 1.977 g 0.820 g 0.480 gExample 10 (Sr_(0.98)Eu_(0.02))₃AlSi₃N₇ 8.681 g 0.211 g 2.965 g 0.820 g0.721 g Example 11 (Sr_(0.98)Eu_(0.02))₄AlSi₄N₉ 11.574 g  0.282 g 3.953g 0.820 g 0.961 g Example 12 (Sr_(0.98)Eu_(0.02))₃Al₂Si₃N₈ 8.681 g 0.211g 2.965 g 1.639 g 0.721 g Example 13 (Sr_(0.98)Eu_(0.02))₃AlSi₆N₁₁ 8.681g 0.211 g 5.930 g 0.820 g 0.721 g Example 14(Sr_(0.98)Eu_(0.02))₅AlSi₁₁N₁₉ 14.468 g  0.352 g 10.872 g  0.820 g 1.201g Example 15 (Sr_(0.98)Eu_(0.02))₇AlSi₁₆N₂₇ 20.255 g  0.493 g 15.814 g 0.820 g 1.682 g Example 16 (Sr_(0.98)Eu_(0.02))₄Al₂Si₇N₁₄ 11.574 g 0.282 g 6.919 g 1.639 g 0.961 g Example 17 (Sr_(0.98)Eu_(0.02))₂AlSi₈N₁₃5.787 g 0.141 g 7.907 g 0.820 g 0.480 g Example 18(Sr_(0.98)Eu_(0.02))₃AlSi₁₅N₂₃ 8.681 g 0.211 g 14.825 g  0.820 g 0.721 gExample 19 (Sr_(0.98)Eu_(0.02))₄AlSi₂₂N₃₃ 11.574 g  0.282 g 21.744 g 0.820 g 0.961 g Example 20 (Sr_(0.98)Eu_(0.02))₃Al₂Si₉N₁₆ 8.681 g 0.211g 8.895 g 1.639 g 0.721 g Example 21 (Sr_(0.98)Eu_(0.02))AlSi₁₀N₁₅ 2.894g 0.070 g 9.884 g 0.820 g 0.240 g Example 22(Sr_(0.98)Eu_(0.02))₃Al₂Si₉N₁₆ 8.681 g 0.211 g 8.895 g 1.639 g 0.721 gExample 23 (Sr_(0.98)Eu_(0.02))₅Al₂Si₁₄N₂₄ 14.468 g  0.352 g 13.837 g 1.639 g 1.201 g Example 24 (Sr_(0.98)Eu_(0.02))₇Al₂Si₁₉N₃₂ 20.255 g 0.493 g 18.779 g  1.639 g 1.682 g Example 25(Sr_(0.98)Eu_(0.02))₉Al₂Si₂₄N₄₀ 26.042 g  0.633 g 23.721 g  1.639 g2.162 g Comparative (Sr_(0.98)Eu_(0.02))Al₂SiN₄ 2.894 g 0.070 g 0.988 g1.639 g 0.240 g Example 1 Comparative (Sr_(0.98)Eu_(0.02))Al₃SiN₅ 2.894g 0.070 g 0.988 g 2.459 g 0.240 g Example 2 Comparative(Sr_(0.98)Eu_(0.02))₂Al₃Si₂N₇ 5.787 g 0.141 g 1.977 g 2.459 g 0.480 gExample 3 Comparative (Sr_(0.98)Eu_(0.02))Al₂Si₄N₈ 2.894 g 0.070 g 3.953g 1.639 g 0.240 g Example 4 Comparative (Sr_(0.98)Eu_(0.02))₂Si₅N₈14.468 g  0.352 g 12.355 g     0 g 1.201 g Example 5

Hereinafter, the characteristics of the phosphor compositions thusobtained will be described briefly.

The body colors of the phosphor compositions of the present example wereall orange. An emission spectrum and an excitation spectrum are omittedherein. The phosphor compositions of Examples 9 to 25 were all redphosphors having an emission peak in the vicinity of a wavelength of 620nm to 640 nm in the same way as in the phosphor of Example 1 or 2 shownin FIG. 15 or 27, which were excited with light in a large wavelengthrange of 220 nm to 600 nm (i.e., ultraviolet light-near-ultravioletlight-violet light-blue light-green light-yellow light-orange light).

For reference, Table 7 shows a summary of an emission peak wavelengthand an absolute value of an emission peak height of the phosphorcompositions of Examples 9 to 25 and Comparative Examples 1 to 5.

TABLE 7 Emission peak Relative emission wavelength peak height (nm)(arbitrary unit) Example 9 639 39 Example 10 626 38 Example 11 629 38Example 12 639 40 Example 13 625 97 Example 14 630 100 Example 15 628 86Example 16 628 92 Example 17 631 73 Example 18 628 67 Example 19 628 66Example 20 626 54 Example 21 638 55 Example 22 625 60 Example 23 630 67Example 24 625 82 Example 25 628 92 Comparative 490 69 Example 1Comparative 484 79 Example 2 Comparative 487 99 Example 3 Comparative594 12 Example 4 Comparative 621 104 Example 5

Furthermore, FIG. 28 is a ternary system of composition showing acomposition range of the phosphor compositions of the present invention.In FIG. 28, regarding the emission colors of the phosphor compositionsof Examples 1, 2, and 5-25, and the phosphor compositions of ComparativeExamples 1-5, ● represents red color, and Δ represents the colors otherthan the red color.

In FIG. 28, ◯ represents a conventional Sr₂Si₅N₈:Eu²⁺ nitridosilicatephosphor emitting red light. Furthermore, in FIG. 28, ⋄ represents aSr₃Al₂N₅:Eu²⁺ phosphor composition that is unstable chemically in theatmosphere and cannot be substantially evaluated for emissioncharacteristics. Furthermore, in the case of using the productioncondition of Example 2, the compositions containing Sr₃N₂ in a highratio in the ternary system of composition shown in FIG. 28 tended to bedifficult to produce due to melting, and unstable chemically in theatmosphere.

It is understood from FIG. 28 and Table 7 that, as a phosphorcomposition different from the conventional nitridosilicate phosphor(e.g., Sr₂Si₅N₈:Eu²⁺), a phosphor composition, which contains acomposition represented by a composition formula: aSr₃N₂.bAlN.cSi₃N₄ asa main component of a phosphor host, and contains Eu²⁺ ions as anactivator, wherein “a”, “b”, and “c” are numerical values satisfying0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, and 0.4≦c/(c+a)≦0.95, becomes a redphosphor.

The phosphor composition characteristic in terms of the constituentcomposition, compared with the above-mentioned conventionalnitridosilicate phosphor, is the one with “a”, “b”, and “c” being thenumerical values satisfying 0.2≦a/(a+b)≦0.6, 0.3≦b/(b+c)≦0.8, and0.4≦c/(c+a)≦0.8; in particular, 0.2≦a/(a+b)≦0.3, 0.6≦b/(b+c)≦0.8, and0.4≦c/(c+a)≦0.6, represented by the composition formula: SrAlSiN₃containing Eu²⁺ ions as an activator.

In Examples 9 to 25, the case of the phosphor composition produced bythe same production method as that shown in Example 2 has beendescribed. Even according to the production method for allowing nitridematerials to react directly with each other shown in Example 1, the sameresults are obtained.

Furthermore, in Examples 9 to 25, the case where the element “M” is setto be Sr has been described. Even in the case where “M” is Ca, and wherethe main component of “M” is set to be Ca or Sr, and a part of “M” isreplaced by Ba, Mg, or Zn, the same results are obtained.

Next, another embodiment of the present invention will be described.

The characteristics of the phosphor activated with Eu²⁺ wereinvestigated in detail. Consequently, the following was found. Thephosphors shown in the following (1) to (3) have a high internal quantumefficiency under the excitation of a blue light-emitting element havingan emission peak in a blue wavelength range of 420 nm to less than 500nm, in particular, 440 nm to less than 500 nm, as well as a highinternal quantum efficiency under the excitation of a violetlight-emitting element having an emission peak in anear-ultraviolet-violet range wavelength range of 360 nm to less than420 nm. Satisfactory phosphors have an internal quantum efficiency of90% to 100%.

(1) A green phosphor of an alkaline-earth metal orthosilicate type, athiogallate type, an aluminate type, and a nitride type (nitridosilicatetype, SIALON type, etc.) activated with Eu²⁺ and having an emission peakin a wavelength range of 500 nm to less than 560 nm (e.g., phosphorssuch as (Ba, Sr)₂SiO₄:Eu²⁺, SrGa₂S₄:Eu²⁺, SrAl₂O₄:Eu²⁺, BaSiN₂:Eu²⁺, andSr_(1.5)Al₃Si₉N₁₆:Eu²⁺).

(2) A yellow phosphor of an alkaline-earth metal orthosilicate type, athiogallate type, and a nitride type nitridosilicate type, SIALON type,etc.) activated with Eu²⁺ and having an emission peak in a wavelengthrange of 560 nm to less than 600 nm (e.g., phosphors such as (Sr,Ba)₂SiO₄:Eu²⁺, CaGa₂S₄:Eu²⁺, 0.75(Ca_(0.9)Eu_(0.1))O.2.25AlN.3.25Si₃N₄:Eu²⁺, Ca_(1.5)Al₃Si₉N₁₆:Eu²⁺, (Sr, Ca)₂SiO₄:Eu²⁺,CaSiAl₂O₃N₂:Eu²⁺, and CaSi₆AlON₉:Eu²⁺).

(3) A red phosphor of a nitride type (nitridosilicate type,nitridoaluminosilicate type) activated with Eu²⁺ and having an emissionpeak in a wavelength range of 600 nm to less than 660 nm (e.g.,phosphors such as Sr₂Si₅N₈:Eu²⁺, SrSiN₂:Eu²⁺, SrAlSiN₃:Eu²⁺,CaAlSiN₃:Eu²⁺, and Sr₂Si₄AlON₇:Eu²⁺).

The excitation spectra of these phosphors have an excitation peak in awavelength range shorter than the wavelength of light emitted by theblue light-emitting element, mostly in a near-ultraviolet-violetwavelength range of 360 nm to less than 420 nm. Therefore, the externalquantum efficiency under the excitation of the blue light-emittingelement is not necessarily high. However, the internal quantumefficiency is found to be at least 70% that is higher than expected fromthe excitation spectrum, and 90% to 100% in a particularly preferablecase.

As an example, FIG. 29 shows an internal quantum efficiency 40, anexternal quantum efficiency 41, and an excitation spectrum 42 of aSrSiN₂:Eu²⁺ red phosphor, and for reference, an emission spectrum 43 ofthe phosphor. FIGS. 30 to 35 respectively show the internal quantumefficiency 40, the external quantum efficiency 41, and the excitationspectrum 42, and for reference, the emission spectrum 43 in the same wayas in FIG. 29, regarding a SrAlSiN₃:Eu²⁺ red phosphor (FIG. 30), aSr₂Si₅N₈:Eu²⁺ red phosphor (FIG. 31), a (Ba, Sr)₂SiO₄:Eu²⁺ greenphosphor (FIG. 32), a (Sr, Ba)₂SiO₄:Eu²⁺ yellow phosphor (FIG. 33), a(Sr, Ca)₂SiO₄:Eu²⁺ yellow phosphor (FIG. 34), and a0.75(Ca_(0.9)Eu_(0.1))O.2.25AlN.3.25Si₃N₄:Eu²⁺ yellow phosphor (FIG.35). For example, the external quantum efficiency of the (Sr,Ba)₂SiO₄:Eu²⁺ yellow phosphor that is an alkaline-earth metalorthosilicate phosphor activated with Eu²⁺ shown in FIG. 33 is about 75%under the excitation of a blue light-emitting element with a wavelengthof 440 nm, about 67% at a wavelength of 460 nm, and about 60% at awavelength of 470 nm. However, in the blue wavelength range of 440 nm toless than 500 nm, the internal quantum efficiency is found to be atleast 85% that is higher than expected from an excitation spectrum, andabout 94% in a particularly satisfactory case.

Furthermore, in addition to the above-mentioned phosphors, a phosphorcoactivated with Eu²⁺ or Ce³⁺ also is found to have the samecharacteristics. As an example, FIGS. 36 to 39 show the internal quantumefficiency 40, the external quantum efficiency 41, and the excitationspectrum 42, and for reference, the emission spectrum 43 in the same wayas in FIG. 29, regarding a (Y, Gd)₃Al₅O₁₂:Ce³⁺ yellow phosphor (FIG.36), a BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (FIG. 37), a Sr₄Al₁₄O₂₅:Eu²⁺blue-green phosphor (FIG. 38), and a (Sr, Ba)₁₀(PO₄)₆Cl₂:Eu²⁺ bluephosphor (FIG. 39).

The following is understood from FIGS. 29 to 39. The excitationwavelength dependency of an external quantum efficiency of each phosphoris similar to the shape of an excitation spectrum. The external quantumefficiency is not necessarily high under the excitation of light with awavelength longer than that of a peak of an excitation spectrum (forexample, under the excitation of a blue light-emitting element);however, the internal quantum efficiency exhibits a high numerical valueunder the excitation of the blue light-emitting element. Furthermore, itis understood from FIGS. 29 to 35 and FIGS. 37 to 39 that each phosphorhas a high internal quantum efficiency under the excitation of theabove-mentioned violet light-emitting element, and the satisfactoryphosphors have an internal quantum efficiency of 90% to 100%.

Further investigation found the following. In addition to theabove-mentioned phosphors (1) to (3), the following phosphors (4) and(5) have a high internal quantum efficiency under the excitation of theviolet light-emitting element.

(4) A nitride type (nitridosilicate type, SIALON type, etc.) blue orgreen phosphor activated with Eu²⁺ or Ce³⁺ and having an emission peakin a wavelength range of 490 nm to 550 nm (e.g., phosphors such asSr₂Si₅N₈:Ce³⁺, SrSiAl₂O₃N₂:Eu²⁺, and Ca_(1.5)Al₃Si₉N₁₆:Ce³⁺).

(5) A blue-green or blue phosphor of an alkaline-earth metalorthosilicate type or a halophosphate type activated with Eu²⁺ andhaving an emission peak in a wavelength range of 420 nm to less than 500nm (e.g., phosphors such as Ba₃MgSi₂O₈:Eu²⁺, and (Sr,Ca)₁₀(PO₄)₆Cl₂:Eu²⁺).

The excitation spectra of these phosphors have an excitation peak in anear-ultraviolet-violet wavelength range of 360 nm to less than 420 nm,so that the external quantum efficiency under the excitation of theviolet light-emitting element is not high.

As an example, FIG. 40 shows the internal quantum efficiency 40, theexternal quantum efficiency 41, and the excitation spectrum 42 of aLa₂O₂S:Eu³⁺ red phosphor frequently used in combination with theabove-mentioned conventional violet light-emitting element, and forreference, the emission spectrum 43 of the phosphor. As is understoodfrom FIG. 40, the internal quantum efficiency and the external quantumefficiency of the above-mentioned La₂O₂S:Eu³⁺ red phosphor decreaserapidly with the increase in an excitation wavelength, in a violet rangein which the peak of the excitation spectrum is 380 nm to less than 420nm, and furthermore in an excitation wavelength of about 360 to 380 nmor more. For example, in the case where the excitation wavelength isprolonged gradually in a violet wavelength range of 380 nm to less than420 nm, the internal quantum efficiency changes greatly at a low level(about 80% (380 nm), about 62% (400 nm), about 25% (420 nm)).

Although data is omitted, the internal quantum efficiency, the externalquantum efficiency and the excitation spectrum of the Y₂O₂S:Eu³⁺ redphosphor correspond to the characteristics of the internal quantumefficiency, the external quantum efficiency, and the excitation spectrumof the above-mentioned La₂O₂S:Eu³⁺ shifted to a short wavelength side by10 to 50 nm.

More specifically, it is understood that the La₂O₂S:Eu³⁺ red phosphorand the Y₂O₂S:Eu³⁺ red phosphor frequently used in combination with theabove-mentioned conventional violet light-emitting element havedifficulty in converting light emitted by a light-emitting elementhaving an emission peak in a near-ultraviolet-violet wavelength range of360 nm to less than 420 nm, in particular, in a violet wavelength rangeof 380 nm to less than 420 nm into red light at a high conversionefficiency, in terms of the physical properties of the material.

The reason why the above-mentioned La₂O₂S:Eu³⁺ red phosphor and theY₂O₂S:Eu³⁺ red phosphor exhibit the above-mentioned excitationwavelength dependency of an internal quantum efficiency is as follows.In the case where Eu³⁺ is excited in the charge transfer state (CTS),and these phosphors emit light after the excitation energy is relaxed toa 4f energy level of Eu³⁺ via the CTS, light emission with a highefficiency is obtained, and in the case where these phosphors emit lightdirectly by the excitation of Eu³⁺ without the CTS, light emission witha high efficiency is not obtained. The above-mentioned CTS refers to thestate where one electron is transferred from the surrounding anions (Oor S) to Eu³⁺. Due to the above-mentioned mechanism, it is difficult toobtain a light-emitting device with a high luminous flux, using theabove-mentioned red phosphor of an oxysulfide type and thelight-emitting element (in particular, a violet light-emitting element).

Furthermore, in the case of configuring a white light-emitting devicethat excites a plurality of kinds of phosphors using a violetlight-emitting element, due to the color balance, the intensity of theoutput light has a correlation with an internal quantum efficiency of aphosphor having a lowest internal quantum efficiency. That is, if atleast one phosphor having a low internal quantum efficiency is presentin a phosphor constituting the light-emitting device, the intensity ofoutput light becomes low, which makes it difficult to obtain white lightwith a high luminous flux.

Herein, the internal quantum efficiency refers to a ratio of the quantumnumber of light emitted by a phosphor, with respect to the quantumnumber of excited light absorbed by the phosphor. The external quantumefficiency refers to a ratio of the quantum number of light emitted by aphosphor, with respect to the quantum number of excited lightilluminating the phosphor. More specifically, a high quantum efficiencyrepresents that excited light is converted efficiently. A method formeasuring a quantum efficiency has already been established, andPublication of Illuminating Engineering Institute of Japan describes thedetail thereof.

The light emitted by a light-emitting element absorbed by a phosphorwith a high internal quantum efficiency is converted efficiently to beoutput. On the other hand, the light emitted by a light-emitting elementthat is not absorbed by the phosphor is output as it is. Therefore, alight-emitting device including a light-emitting element having anemission peak in the above-mentioned wavelength range and a phosphorhaving a high internal quantum efficiency under the excitation of lightemitted by the light-emitting element can use light energy efficiently.Thus, by combining at least the above-mentioned phosphors (1) to (5)with the above-mentioned light-emitting element, a light-emitting devicewith a high luminous flux and a high color rendering property can beobtained.

On the other hand, a light-emitting device including a light-emittingelement having an emission peak in the above-mentioned wavelength range,and a phosphor having a low internal quantum efficiency under theexcitation of light emitted by the light-emitting element cannot convertlight energy emitted by the light-emitting element efficiently, andhence has a low luminous flux.

A light-emitting device including a light-emitting element having anemission peak in a near-ultraviolet-violet wavelength range of 360 nm toless than 420 nm, and a phosphor having a low external quantumefficiency under the excitation of light emitted by the light-emittingelement emits light in a near-ultraviolet-violet wavelength range thathas a low spectral luminous efficacy and hardly participates in theenhancement of a luminous flux. Therefore, unless light emitted by thelight-emitting element is allowed to be absorbed in a large amount by aphosphor, by increasing the thickness of the phosphor layer, enhancingthe concentration of a phosphor in the phosphor layer, etc., a luminousflux becomes low.

Hereinafter, another embodiment of the light-emitting device of thepresent invention will be described.

Embodiment 6

An example of a light-emitting device of the present invention includesa phosphor layer containing a nitride phosphor and a light-emittingelement. The light-emitting element has an emission peak in a wavelengthrange of 360 nm to less than 500 nm, the nitride phosphor is excitedwith light emitted by the light-emitting element to emit light, and thelight-emitting device contains at least light-emitting component lightemitted by the nitride phosphor as output light. Furthermore, thenitride phosphor is activated with Eu²⁺ and represented by a compositionformula: (M_(1-x)Eu_(x))AlSiN₃, where “M” is at least one elementselected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and “x” isa numerical value satisfying 0.005≦x≦0.3.

The light-emitting element is not particularly limited, as long as it isa photoelectric transducer for converting electric energy into light,which emits light having an emission peak in any of wavelength ranges of360 nm to less than 420 nm or 420 nm to less than 500 nm, morepreferably 380 nm to less than 420 nm or 440 nm to less than 500 nm. Forexample, a light-emitting diode (LED), a laser diode (LD), asurface-emitting LD, an inorganic electroluminescence (EL) element, anorganic EL element, or the like can be used.

In the case of using, as a light-emitting element, an LED or an LDincluding a GaN-based compound as a light-emitting layer, it ispreferable to use a violet light-emitting element that emits lighthaving an emission peak in a wavelength range of preferably 380 nm toless than 420 nm, more preferably 395 nm to 415 nm, or a bluelight-emitting element that emits light having an emission peak in awavelength range of preferably 440 nm to less than 500 nm, morepreferably 450 nm to 480 nm, since a high output is obtained.

It is preferable that the output light contains light-emitting componentlight emitted by the light-emitting element. In particular, in the casewhere the above-mentioned light-emitting element has an emission peak ina blue wavelength range, if light-emitting component light emitted bythe nitride phosphor and light-emitting component light emitted by theemission element are included in output light, white light having ahigher color rendering property is obtained, which is more preferable.

The above-mentioned nitride phosphor is represented by theabove-mentioned composition formula: (M_(1-x)Eu_(x))AlSiN₃, which emitslight in a warm color having an emission peak in a wavelength range of600 nm to less than 660 nm, preferably red light having an emission peakin a wavelength range of 610 nm to 650 nm. The above-mentioned nitridephosphor corresponds to a nitride phosphor having a high internalquantum efficiency under the excitation of light in a wavelength rangeof 360 nm to less than 500 nm, for example, the SrAlSiN₃:Eu²⁺ redphosphor, the CaAlSiN₃:Eu²⁺ red phosphor, and the like shown in FIG. 30.

The light-emitting device including at least a phosphor layer containinga nitride phosphor with a high internal quantum efficiency and theabove-mentioned light-emitting element can output light energyefficiently. The light-emitting device configured as described above hasa high intensity of a light-emitting component in a warm color, and aspecial color rendering index R9 with a large numerical value. Thislight-emitting device has a high luminous flux and a high colorrendering property, comparable to those of a conventional light-emittingdevice using a La₂O₂S:Eu³⁺ phosphor and a conventional light-emittingdevice using a combination of a Sr₂Si₅N₈:Eu²⁺ phosphor and a YAG:Cephosphor.

The light-emitting device of the present embodiment is not particularlylimited, as long as it includes at least a phosphor layer containing theabove-mentioned nitride phosphor and the above-mentioned light-emittingelement. For example, the light-emitting device of the presentembodiment corresponds to a semiconductor light-emitting device, a whiteLED, a display device using a white LED, an illumination device using awhite LED, etc. More specifically, examples of the display device usinga white LED include an LED information display terminal, an LED trafficlight, and an LED lamp for an automobile. Examples of the illuminationdevice using a white LED include an LED indoor-outdoor illuminationlamp, an interior LED lamp, an LED emergency lamp, and an LED decorativelamp.

Among them, the above-mentioned white LED is particularly preferable. Ingeneral, a conventional LED is a light-emitting element of amonochromatic light source that emits light having a particularwavelength from the light emission principle. That is, a light-emittingelement that emits white light cannot be obtained from the conventionalLED. In contrast, white fluorescence can be obtained from the white LEDof the present embodiment by a method for combining, for example, theconventional LED and a phosphor.

In the present embodiment, when the main component of the element “M” isset to be Sr or Ca, the nitride phosphor obtains a satisfactory colortone and a high emission intensity, which is more preferable. Settingthe main component to be Sr or Ca means that at least 50 atomic % of theelement “M” is any one element of Sr and Ca. Furthermore, it ispreferable that at least 80 atomic % of the element “M” is any oneelement of Sr and Ca, and it is more preferable that all the atoms ofthe element “M” are any one element of Sr and Ca.

Furthermore, it is preferable that the above-mentioned injection typeelectroluminescence element is used, since the light-emitting elementemits a strong output light. It is more preferable that an LED or an LDparticularly containing a GaN-based semiconductor in an active layer isused as an injection type electroluminescence element, since strongstable output light is obtained.

Embodiment 7

As another example of the light-emitting device of the presentinvention, the above-mentioned phosphor layer of Embodiment 6 mayfurther contain a green phosphor that is activated with Eu²⁺ or Ce³⁺ andhas an emission peak in a wavelength range of 500 nm to less than 560nm. The green phosphor is not particularly limited, as long as it isexcited with light emitted by the light-emitting element described inEmbodiment 6, and emits light having an emission peak in a wavelengthrange of 500 nm to less than 560 nm, preferably 510 nm to 550 nm, andmore preferably 525 nm to 550 nm.

For example, in the case of using a blue light-emitting element, it maybe possible to use a green phosphor in which an excitation peak of anexcitation spectrum on a longest wavelength side is not in a wavelengthrange of 420 nm to less than 500 nm (i.e., an excitation peak of anexcitation spectrum on a longest wavelength side is in a wavelengthrange of less than 420 nm).

The green phosphor corresponds to a phosphor having an internal quantumefficiency under the excitation of light in a wavelength range of 360 nmto less than 500 nm, for example, the (Ba, Sr)₂SiO₄:Eu²⁺ green phosphorshown in FIG. 32 or the like. A light-emitting device including at leasta phosphor layer containing at least the phosphor and theabove-mentioned light-emitting element is preferable, since it outputslight energy efficiently. In such a light-emitting device, the emissionintensity of green light contained in output light increases and thecolor rendering property is enhanced. Furthermore, green light has ahigh excitation energy efficacy and a higher luminous flux. Inparticular, depending upon the combination of a phosphor contained in aphosphor layer, it is possible to obtain output light having a highcolor rendering property with an average color rendering index Ra of atleast 90.

It is more preferable that the above-mentioned green phosphor is anitride phosphor or an oxynitride phosphor activated with Eu²⁺ (e.g.,BaSiN₂:Eu²⁺, Sr_(1.5)Al₃Si₉N₁₆:Eu²⁺, Ca_(1.5)Al₃Si₉N₁₆:Eu²⁺,CaSiAl₂O₃N₂:Eu²⁺, SrSiAl₂O₃N₂:Eu²⁺, CaSi₂O₂N₂:Eu²⁺, SrSi₂O₂N₂:Eu²⁺,BaSi₂O₂N₂:Eu²⁺), an alkaline-earth metal orthosilicate phosphoractivated with Eu²⁺ (e.g., (Ba, Sr)₂SiO₄:Eu²⁺, (Ba, Ca)₂SiO₄:Eu²⁺), athiogallate phosphor activated with Eu²⁺ (e.g., SrGa₂S₄:Eu²⁺), analuminate phosphor activated with Eu²⁺ (e.g., SrAl₂O₄:Eu²⁺), analuminate phosphor coactivated with Eu²⁺ and Mn²⁺ (e.g.,BaMgAl₁₀O₁₇:Eu²⁺, Mn²⁺), a nitride phosphor or an oxynitride phosphoractivated with Ce³⁺ (e.g., Sr₂Si₅N₈:Ce³⁺, Ca_(1.5)Al₃Si₉N₁₆:Ce³⁺,Ca₂Si₅N₈:Ce³⁺), and a phosphor having a garnet configuration activatedwith Ce³⁺ (e.g., Y₃(Al, Ga)₅O₁₂:Ce³⁺, Y₃Al₅O₁₂:Ce³⁺, BaY₂SiAl₄O₁₂:Ce³⁺,Ca₃Sc₂Si₃O₁₂:Ce³⁺), since the internal quantum efficiency under theexcitation of the above-mentioned light-emitting element becomes high.

Thus, the light-emitting device of the present embodiment includes aphosphor layer containing at least the nitride phosphor of Embodiment 6and the above-mentioned green phosphor, and the light-emitting elementof Embodiment 6, and contains red light-emitting component light emittedby the nitride phosphor and green light-emitting component light emittedby the green phosphor as output light.

Embodiment 8

As still another example of the light-emitting device of the presentinvention, the phosphor layer of Embodiment 6 or 7 further may contain ayellow phosphor activated with Eu²⁺ or Ce³⁺ and having an emission peakin a wavelength range of 560 nm to less than 600 nm. The yellow phosphoris not particularly limited as long as it is excited with light emittedby the light-emitting element described in Embodiment 6, and emits lighthaving an emission peak in a wavelength range of 560 nm to less than 600nm, preferably 565 nm to 580 nm.

For example, in the case of using a blue light-emitting element, ayellow phosphor whose excitation peak of an excitation spectrum on alongest wavelength side is not in a wavelength range of 420 nm to lessthan 500 nm (i.e., a yellow phosphor whose excitation peak of anexcitation spectrum on a longest wavelength side is in a wavelengthrange of less than 420 nm) may be used.

The above-mentioned yellow phosphor corresponds to a phosphor having aninternal quantum efficiency under the excitation of light in awavelength range of 360 nm to less than 500 nm (e.g., a (Sr,Ba)₂SiO₄:Eu²⁺ yellow phosphor shown in FIG. 33, a (Sr, Ca)₂SiO₄:Eu²⁺yellow phosphor shown in FIG. 34, a 0.75CaO.2.25 AlN.3.25 Si₃N₄:Eu²⁺yellow phosphor shown in FIG. 35), and a phosphor having a high internalquantum efficiency under the excitation of light in a wavelength rangeof 420 nm to less than 500 nm (e.g., a (Y, Gd)₃Al₅O₁₂:Ce³⁺ yellowphosphor shown in FIG. 36). A light-emitting device including at least aphosphor layer containing at least this phosphor and the above-mentionedlight-emitting element is preferable since it outputs light energyefficiently. This light-emitting device has a high emission intensity ofyellow light contained in output light and an enhanced color renderingproperty, and emits light, particularly in mild color or warm color.Furthermore, yellow light has relatively high spectral luminousefficacy, and a high luminous flux. In particular, depending upon thematerial design of the phosphor layer, it is possible to obtain outputlight having a high color rendering property with Ra of at least 90.

It is further preferable to use, as the above-mentioned yellow phosphor,a nitride phosphor or an oxynitride phosphor activated with Eu²⁺ (e.g.,0.75CaO.2.25AlN.3.25Si₃N₄:Eu²⁺, Ca_(1.5)Al₃Si₉N₁₆:Eu²⁺,CaSiAl₂O₃N₂:Eu²⁺, CaSi₆AlON₉:Eu²⁺), an alkaline-earth metalorthosilicate phosphor activated with Eu²⁺ (e.g., (Sr, Ba)₂SiO₄:Eu²⁺,(Sr, Ca)₂SiO₄:Eu²⁺), a thiogallate phosphor activated with Eu²⁺ (e.g.,CaGa₂S₄:Eu²⁺), and a phosphor having a garnet configuration activatedwith Ce³⁺ (e.g., (Y, Gd)₃Al₅O₁₂:Ce³⁺) since the internal quantumefficiency under the excitation of the above-mentioned light-emittingelement becomes high.

Thus, the light-emitting device of the present embodiment includes aphosphor layer containing at least the nitride phosphor of Embodiment 6and the yellow phosphor, and the light-emitting element of Embodiment 6,and contains red light-emitting component light emitted by the nitridephosphor and yellow light-emitting component light emitted by the yellowphosphor in output light.

Embodiment 9

As still another example of the light-emitting device of the presentinvention, the phosphor layer described in any of Embodiments 6 to 8further may contain a blue phosphor activated with Eu²⁺ and having anemission peak in a wavelength range of 420 nm to less than 500 nm. Theblue phosphor is not particularly limited as long as it is excited withlight emitted by the light-emitting element described in Embodiment 6,and emits light having an emission peak in a wavelength range of 420 nmto less than 500 nm, preferably 440 nm to 480 nm in terms of the colorrendering property and the output. In this case, the light-emittingelement is not particularly limited as long as it is the one describedin Embodiment 6; however, it is preferable to use a violetlight-emitting element for the following reason. The range of choices ofa phosphor ingredient is extended, so that it is easy to design thecolor of light emitted by the light-emitting device, and even when thewavelength position of light emitted by the light-emitting elementvaries depending upon the driving condition such as the power for thelight-emitting element, the influence on output light is small.

The above-mentioned blue phosphor corresponds to a phosphor having ahigh internal quantum efficiency under the excitation of light in awavelength range of 360 nm to less than 500 nm, preferably 360 nm toless than 420 nm (e.g., a BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor shown in FIG.37, a Sr₄Al₁₄O₂₅:Eu²⁺ blue phosphor shown in FIG. 38, a (Sr,Ba)₁₀(PO₄)₆Cl₂:Eu²⁺ blue phosphor shown in FIG. 39). A light-emittingdevice including at least a phosphor layer containing this phosphor andthe above-mentioned light-emitting element is preferable since itoutputs light energy efficiently. This light-emitting device has a highintensity of blue emission contained in output light, an enhanced colorrendering property, and a high luminous flux. In particular, dependingupon the material design of the phosphor layer, it is possible to obtainoutput light having a high color rendering property with Ra of at least90, and it is possible to obtain white output light close to thesunlight with all the special color rendering indexes R1 to R15 of atleast 80, preferably at least 85, and more preferably at least 90. Forexample, by using BaMgAl₁₀O₁₇:Eu²⁺, (Sr, Ba)₁₀(PO₄)₆Cl₂:Eu²⁺,Ba₃MgSi₂O₈:Eu²⁺, SrMgAl₁₀O₁₇:Eu²⁺, (Sr, Ca)₁₀(PO₄)₆Cl₂:Eu²⁺,Ba₅SiO₄Cl₆:Eu²⁺, BaAl₈O_(1.5):Eu²⁺, Sr₁₀(PO₄)₆Cl₂:Eu²⁺, a blue phosphor,etc., output light having the above-mentioned high color renderingproperty and special color rendering index can be obtained.

Furthermore, it is further preferable to use, as the above-mentionedblue phosphor, a nitride phosphor or an oxynitride phosphor activatedwith Eu²⁺ (e.g., SrSiAl₂O₃N₂:Eu²⁺), an alkaline-earth metalorthosilicate phosphor activated with Eu²⁺ (e.g., Ba₃MgSi₂O₈:Eu²⁺,Sr₃MgSi₂O₈:Eu²⁺), an aluminate phosphor activated with Eu²⁺ (e.g.,BaMgAl₁₀O₁₇:Eu²⁺, BaAl₈O₁₃:Eu²⁺, Sr₁₄O₂₅:Eu²⁺), and a halophosphatephosphor activated with Eu²⁺ (e.g., Sr₁₀(PO₄)₆Cl₂:Eu²⁺), (Sr,Ca)₁₀(PO₄)₆Cl₂:Eu²⁺, (Ba, Ca, Mg)₁₀(PO₄)₆Cl₂:Eu²⁺), since the internalquantum efficiency under the excitation of the above-mentionedlight-emitting element becomes high.

In Embodiments 6 to 9, in order to obtain a high luminous flux, it ispreferable that the phosphor contained in the above-mentioned phosphorlayer does not substantially contain a phosphor other than the phosphoractivated with Eu²⁺ or Ce³⁺, and does not substantially contain aninorganic phosphor other than a nitride phosphor or an oxynitridephosphor. The configuration that does not substantially contain aphosphor other than the phosphor activated with Eu²⁺ or Ce³⁺ means thatat least 90% by weight, preferably at least 95% by weight, and morepreferably at least 98% by weight of the phosphor contained in thephosphor layer is a phosphor activated with Eu²⁺ or Ce³⁺. Furthermore,the configuration that does not substantially contain an inorganicphosphor other than a nitride phosphor or an oxynitride phosphor meansthat at least 90% by weight, preferably at least 95% by weight, and morepreferably at least 98% by weight of the phosphor contained in thephosphor layer is a nitride phosphor or an oxynitride phosphor. Theabove-mentioned nitride phosphor or oxynitride phosphor holds arelatively high internal quantum efficiency even at an operationtemperature and an environmental temperature of 100° C. to 150° C., andthe peak of a wavelength of an emission spectrum does not shift to ashort wavelength side, for example, as in the above-mentionedalkaline-earth metal orthosilicate phosphor or phosphor having a garnetconfiguration. Therefore, even when the power is increased to enhancethe intensity of excited light of the light-emitting device with theabove configuration, or even when the light-emitting device is used in ahigh temperature atmosphere, the emission color varies less, wherebystable output light is obtained.

In order to obtain a light-emitting device emitting a high luminousflux, a phosphor having a lowest internal quantum efficiency under theexcitation of light emitted by the light-emitting element, amongphosphors substantially contained in the phosphor layer, is set to havean internal quantum efficiency (absolute value) of at least 80%,preferably at least 85%, and more preferably at least 90%.

Embodiment 10

Still another example of the light-emitting device of the presentinvention includes a phosphor layer containing a phosphor and alight-emitting element. The light-emitting element has an emission peakin a wavelength range of 360 nm to less than 500 nm, and the phosphor isexcited with light emitted by the light-emitting element to emit light.The light-emitting device contains at least light-emitting componentlight emitted by the phosphor as output light. Furthermore, the phosphorcontains a nitride phosphor or an oxynitride phosphor activated withEu²⁺ and having an emission peak in a wavelength range of 600 nm to lessthan 660 nm, and an alkaline-earth metal orthosilicate phosphor excitedwith Eu²⁺ and having an emission peak in a wavelength range of 500 nm toless than 600 nm. Each internal quantum efficiency of these phosphorsunder the excitation of light emitted by the light-emitting element isat least 80%.

As the light-emitting element, the same light-emitting element as thatdescribed in Embodiment 6 can be used.

It is preferable that the output light contains light-emitting componentlight emitted by the light-emitting element. In particular, in the casewhere the light-emitting element has an emission peak in a bluewavelength range, it is preferable that light-emitting component lightemitted by the phosphor and light-emitting component light emitted bythe light-emitting element are contained in output light, since whitelight having a higher color rendering property is obtained.

The above-mentioned nitride phosphor or oxynitride phosphor activatedwith Eu²⁺ corresponds to a phosphor emitting light in a warm colorhaving an emission peak in a wavelength range of 600 nm to less than 660nm, preferably red light having an emission peak in a wavelength rangeof 610 nm to 650 nm, and having a high internal quantum efficiency underthe excitation of light in a wavelength range of 360 nm to less than 500nm. More specifically, a nitridoaluminosilicate phosphor represented bya composition formula: (M_(1-x)Eu_(x))AlSiN₃ (e.g., a SrAlSiN₃:Eu²⁺ redphosphor, a CaAlSiN₈:Eu²⁺ red phosphor shown in FIG. 30), anitridosilicate phosphor represented by a composition formula:(M_(1-x)Eu_(x))SiN₂ (e.g., a SrSiN₂:Eu²⁺ red phosphor or a CaSiN₂:Eu²⁺red phosphor shown in FIG. 29), a nitridosilicate phosphor representedby a composition formula: (M_(1-x)Eu_(x))₂Si₅N₈ (e.g., a Sr₂Si₅N₈:Eu²⁺red phosphor, a Ca₂Si₅N₈:Eu²⁺ red phosphor, or a Ba₂Si₅N₈:Eu²⁺ redphosphor shown in FIG. 31), or an oxonitridoaluminosilicate phosphorrepresented by a composition formula: (M_(1-x)Eu_(x))₂Si₄AlON₇ (e.g., aSr₂Si₄AlON₇:Eu²⁺ red phosphor) may be used. In the above compositionformula, “M” is at least one element selected from the group consistingof Mg, Ca, Sr, Ba, and Zn, and “x” is a numerical value satisfying0.005≦x≦0.3.

Furthermore, the above-mentioned alkaline-earth metal orthosilicatephosphor is activated with Eu²⁺ and has an emission peak in a wavelengthrange of 500 nm to less than 600 nm, preferably 525 nm to less than 600nm. More specifically, the above-mentioned alkaline-earth metalorthosilicate phosphor corresponds to a green phosphor having anemission peak in a wavelength range of 525 nm to less than 560 nm, morepreferably 530 nm to 550 nm (e.g., a (Ba, Sr)₂SiO₄:Eu² green phosphorshown in FIG. 32), or a yellow phosphor having an emission peak in awavelength range of 560 nm to less than 600 nm (e.g., a (Sr,Ba)₂SiO₄:Eu²⁺ yellow phosphor shown in FIG. 33), a (Sr, Ca)₂SiO₄:Eu²⁺yellow phosphor shown in FIG. 34), and having a high internal quantumefficiency under the excitation of light in a wavelength range of 360 nmto less than 500 nm.

The above-mentioned phosphors have an internal quantum efficiency of atleast 80%, preferably at least 85%, and more preferably at least 90%under the excitation of light emitted by the light-emitting element. Alight-emitting device including at least a phosphor layer containing aphosphor having a high internal quantum efficiency as described aboveand the above-mentioned light-emitting element can output light energyefficiently. Furthermore, a light-emitting device configured using theabove-mentioned nitride phosphor or oxynitride phosphor has a highintensity of a light-emitting component in a warm color, and a specialcolor rendering index R9 with a large numerical value.

Furthermore, the light-emitting device with the above-mentionedconfiguration does not use a sulfide phosphor that has a problem interms of the reliability, and uses an expensive nitride phosphor oroxynitride phosphor only as a red phosphor, whereby a white light sourcewith a high luminous flux and a high color rendering property can beprovided, and the cost of a light-emitting device such as a white lightsource can be reduced.

The light-emitting device of the present embodiment is not particularlylimited, as long as it includes at least a phosphor layer containing theabove-mentioned nitride phosphor or oxynitride phosphor that is excitedwith Eu²⁺ to emit red light, and the above-mentioned alkaline-earthmetal orthosilicate phosphor activated with Eu²⁺, and theabove-mentioned light-emitting element. For example, the light-emittingdevice of the present embodiment corresponds to the above-mentionedwhite LED or the like.

In the present embodiment, it is more preferable that the main componentof the above-mentioned element “M” is set to be Sr or Ca, since thenitride phosphor or oxynitride phosphor represented by theabove-mentioned composition formula has a satisfactory color tone and ahigh emission intensity. Setting the main component to be Sr or Ca meansthat at least 50 atomic % of the element “M” is any one element of Srand Ca. Furthermore, it is preferable that at least 80 atomic % of theelement “M” is any one element of Sr and Ca, and it is more preferablethat all the atoms of the element “M” is any one element of Sr and Ca.

Furthermore, it is preferable to use the above-mentioned injection typeelectroluminescence element as the above-mentioned light-emittingelement, since such an element emits strong output light.

It is preferable to use, as the above-mentioned alkaline-earth metalorthosilicate phosphor, a green phosphor activated with Eu²⁺ and havingan emission peak in a wavelength range of 500 nm to less than 560 nm,preferably 525 nm to less than 560 nm, and more preferably 530 nm to 550nm (e.g., (Ba, Sr)₂SiO₄:Eu²⁺, (Ba, Ca)₂SiO₄:Eu²). A light-emittingdevice using this green phosphor has a high emission intensity of greenlight contained in output light, and an enhanced color renderingproperty. Furthermore, green light has high spectral luminous efficacyand a higher luminous flux. In particular, depending upon thecombination of phosphors contained in the phosphor layer, it is possibleto obtain output light having a high color rendering property with Ra ofat least 90.

Furthermore, it is preferable to use, as the above-mentionedalkaline-earth metal orthosilicate phosphor, a yellow phosphor activatedwith Eu²⁺ and having an emission peak in a wavelength range of 560 nm toless than 600 nm, preferably 565 nm to 580 nm (e.g., (Sr,Ba)₂SiO₄:Eu²⁺). A light-emitting device using this yellow phosphor has ahigh emission intensity of yellow light contained in output light, andan enhanced color rendering property. In particular, a light-emittingdevice emitting light in mild color or warm color can be provided.Furthermore, yellow light has relatively high spectral luminous efficacyand a high luminous flux. In particular, depending upon the materialdesign of the phosphor layer, it is possible to obtain output light withRa of at least 90 and a high color rendering property. Furthermore, italso is preferable to use a (Sr, Ca)₂SiO₄:Eu²⁺ yellow phosphor, or thelight emitting fluorescence close to that of the above-mentioned yellowphosphor.

In the present embodiment, it is preferable that a nitride phosphor oran oxynitride phosphor is not substantially contained as a phosphorother than the above-mentioned red phosphor contained in theabove-mentioned phosphor layer. Because of this, the amount of a nitridephosphor or an oxynitride phosphor used in a light-emitting device canbe minimized, and the production cost of the light-emitting device canbe reduced. Furthermore, it is preferable that a sulfide phosphor is notsubstantially contained as a phosphor other than the above-mentioned redphosphor contained in the above-mentioned phosphor layer. This canenhance the reliability of a light-emitting device, and for example, alight-emitting device with less change (e.g., degradation) with time canbe provided.

Even in Embodiment 10, it is preferable that the phosphor contained inthe above-mentioned phosphor layer does not substantially contain aphosphor other than the phosphor activated with Eu²⁺ or Ce³⁺ so as toobtain a high luminous flux. Furthermore, it is preferable that theinternal quantum efficiency of a phosphor having a lowest internalquantum efficiency under the excitation of light emitted by alight-emitting element, among the phosphors substantially contained inthe phosphor layer, is at least 80%.

Hereinafter, light-emitting devices of Embodiments 6 to 10 will bedescribed with reference to FIGS. 1 to 12.

FIGS. 1, 2, and 3 are cross-sectional views of semiconductorlight-emitting devices showing examples of the light-emitting device ofthe present invention.

FIG. 1 shows a semiconductor light-emitting device having aconfiguration in which at least one light-emitting element 1 is mountedon a submount element 4, and the light-emitting element 1 is sealed witha base material that also functions as a phosphor layer 3 containing aphosphor composition 2. FIG. 2 shows a semiconductor light-emittingdevice having a configuration in which at least one light-emittingelement 1 is mounted on a cup 6 provided at a mount lead of a lead frame5, the phosphor layer 3 containing the phosphor composition 2 isprovided in the cup 6, and the entire body is sealed with a sealant 7made of resin or the like. FIG. 3 shows a semiconductor light-emittingelement of a chip type having a configuration in which at least onelight-emitting element 1 is mounted in a housing 8, and the phosphorlayer 3 containing the phosphor composition 2 is provided.

In FIGS. 1 to 3, the light-emitting element 1 is a photoelectrictransducer for converting electric energy into light, and is notparticularly limited as long as it emits light having an emission peakin a wavelength range of 360 nm to less than 500 nm, preferably 380 nmto less than 420 nm or 440 nm to less than 500 nm, and more preferably395 nm to 415 nm or 450 nm to 480 nm. For example, an LED, an LD, asurface-emitting LD, an inorganic EL element, an organic EL element, orthe like may be used. In particular, in order to increase the output ofa semiconductor light-emitting element, an LED or a surface-emitting LEDis preferable.

In FIGS. 1 to 3, the phosphor layer 3 is configured by dispersing, asthe phosphor composition 2, at least a nitride phosphor represented by acomposition formula: (M_(1-x)Eu_(x))AlSiN₃ where “M” is at least oneelement selected from the group consisting of Mg, Ca, Sr, Ba, and Zn,and “x” is a numerical value satisfying 0.005≦x 0.3.

There is no particular limit on a material used for the base material ofthe phosphor layer 3, and in general, transparent resin such as epoxyresin or silicone resin, low-melting glass, or the like may be used. Inorder to provide a light-emitting device having less decrease inemission intensity with the passage of an operation time, theabove-mentioned base material is preferably silicone resin or atranslucent inorganic material such as low-melting glass, and morepreferably the above-mentioned translucent inorganic material. Forexample, in the case of using the transparent resin for the basematerial of the phosphor layer 3, the content of a nitride phosphor ispreferably 5 to 80% by weight, and more preferably 10 to 60% by weight.The nitride phosphor contained in the phosphor layer 3 absorbs a part oran entirety of light emitted by the light-emitting element 1 to convertit into red light. Therefore, light-emitting component light emitted bythe nitride phosphor is contained as output light of the semiconductorlight-emitting device.

Furthermore, in the case where the phosphor layer 3 contains at least anitride phosphor represented by a composition formula:(M_(1-x)Eu_(x))AlSiN₃ as the phosphor composition 2, the phosphor layer3 further may contain a phosphor other than the nitride phosphor. Forexample, when the above-mentioned alkaline-earth metal orthosilicatephosphor, nitride phosphor, oxynitride phosphor, aluminate phosphor,halophosphate phosphor, thiogallate phosphor, and the like, activatedwith Eu²⁺ or Ce³⁺ and having a high internal quantum efficiency underthe excitation of light in a wavelength range of 360 nm to less than 500nm are used in the following phosphor layers (1) to (6), and a violetlight-emitting element having an emission peak in a wavelength range of360 nm to less than 420 nm is used as the light-emitting element 1, aphosphor is excited with light emitted by the light-emitting element 1at a high efficiency, whereby a semiconductor light-emitting element isobtained, which emits white light, for example, owing to the colormixture and the like of light emitted by a plurality of phosphors.

(1) A phosphor layer containing a blue phosphor emitting light having anemission peak in a wavelength range of 420 nm to less than 500 nm,preferably 440 nm to less than 500 nm, a green phosphor emitting lighthaving an emission peak in a wavelength range of 500 nm to less than 560nm, preferably 510 nm to 550 nm, a yellow phosphor emitting light havingan emission peak in a wavelength range of 560 nm to less than 600 nm,preferably 565 nm to 580 nm, and the above-mentioned nitride phosphor.

(2) A phosphor layer containing a blue phosphor emitting light having anemission peak in a wavelength range of 420 nm to less than 500 nm,preferably 440 nm to less than 500 nm, a green phosphor emitting lighthaving an emission peak in a wavelength range of 500 nm to less than 560nm, preferably 510 nm to 550 nm, and the above-mentioned nitridephosphor.

(3) A phosphor layer containing a blue phosphor emitting light having anemission peak in a wavelength range of 420 nm to less than 500 nm,preferably 440 nm to less than 500 nm, a yellow phosphor emitting lighthaving an emission peak in a wavelength range of 560 nm to less than 600nm, preferably 565 nm to 580 nm, and the above-mentioned nitridephosphor.

(4) A phosphor layer containing a green phosphor emitting light havingan emission peak in a wavelength range of 500 nm to less than 560 nm,preferably 525 nm to less than 560 nm, a yellow phosphor emitting lighthaving an emission peak in a wavelength range of 560 nm to less than 600nm, preferably 565 nm to 580 nm, and the above-mentioned nitridephosphor.

(5) A phosphor layer containing the above-mentioned yellow phosphor andthe above-mentioned nitride phosphor.

(6) A phosphor layer containing the above-mentioned green phosphor andthe above-mentioned nitride phosphor.

Furthermore, when the above-mentioned phosphors are used in thefollowing phosphor layers (7) to (9), and a blue light-emitting elementhaving an emission peak in a wavelength range of 420 nm to less than 500nm is used as the light-emitting element 1, a semiconductorlight-emitting device is obtained that emits white light owing to thecolor mixture of light emitted by the light-emitting element 1 and lightemitted by the phosphors, etc.

(7) A phosphor layer containing a green phosphor emitting light havingan emission peak in a wavelength range of 500 nm to less than 560 nm,preferably 525 nm to less than 560 nm, a yellow phosphor emitting lighthaving an emission peak in a wavelength range of 560 nm to less than 600nm, preferably 565 nm to 580 nm, and the above-mentioned nitridephosphor.

(8) A phosphor layer containing the yellow phosphor and theabove-mentioned nitride phosphor.

(9) A phosphor layer containing the green phosphor and theabove-mentioned nitride phosphor.

In the case of using a blue light-emitting element as the light-emittingelement, the green phosphor and the yellow phosphor can be widelyselected from not only an alkaline-earth metal orthosilicate phosphoractivated with Eu²⁺, a nitride phosphor activated with Eu²⁺, and anoxynitride phosphor, but also a phosphor (in particular, a YAG:Cephosphor) having a garnet configuration activated with Ce³⁺, athiogallate phosphor activated with Eu²⁺, and the like. Morespecifically, a SrGa₂S₄:Eu²⁺ green phosphor, a Y₃(Al, Ga)₅O₁₂:Ce³⁺ greenphosphor, a Y₃Al₅O₁₂:Ce³⁺ green phosphor, a BaY₂SiAl₄O₁₂:Ce³⁺ greenphosphor, a Ca₃Sc₂Si₃O₁₂:Ce³⁺ green phosphor, a (Y, Gd)₃Al₅O₁₂:Ce³⁺yellow phosphor, a Y₃Al₅O₁₂:Ce³⁺, Pr³⁺ yellow phosphor, a CaGa₂S₄:Eu²⁺yellow phosphor, or the like can be used.

Alternatively, in FIGS. 1 to 3, the phosphor layer 3 is configured by atleast dispersing, as the phosphor composition 2, a nitride phosphor oran oxynitride phosphor activated with Eu²⁺ and having an emission peakin any wavelength range of 500 nm to less than 560 nm or 560 nm to lessthan 600 nm.

Regarding the phosphor layer 3, the above-mentioned base material may beused. Furthermore, the phosphor composition 2 contained in the phosphorlayer 3 absorbs a part or an entirety of light emitted by thelight-emitting element 1 to convert it into light. Therefore, the outputlight of the semiconductor light-emitting device contains at leastlight-emitting component light emitted by a nitride phosphor or anoxynitride phosphor, and light-emitting component light emitted by analkaline-earth metal orthosilicate phosphor.

Furthermore, even in the case where the phosphor layer 3 contains, asthe phosphor composition 2, a nitride phosphor or an oxynitride phosphorthat is activated with Eu²⁺ to emit red light, and an alkaline-earthmetal orthosilicate phosphor that is activated with Eu²⁺ and has anemission peak in any wavelength range of 500 nm to less than 560 nm or560 nm to less than 600 nm, the phosphor layer 3 further may or may notcontain the above-mentioned nitride phosphor or oxynitride phosphor, anda phosphor other than an alkaline-earth metal orthosilicate phosphor.

For the purpose of reducing the used amount of the nitride phosphor orthe oxynitride phosphor, and the sulfide phosphor, it is preferable thatthe phosphor layer does not contain a nitride phosphor or an oxynitridephosphor other than the above and a sulfide phosphor.

For example, if the above-mentioned aluminate phosphor, halophosphatephosphor, etc. activated with Eu²⁺ or Ce³⁺ and having a high internalquantum efficiency under the excitation of a wavelength range of 360 nmto less than 500 nm, and the above-mentioned phosphor layers (1) to (6)are used in combination, a phosphor is excited with light emitted by thelight-emitting element at a high efficiency, whereby a semiconductorlight-emitting device emits white light owing to the color mixture oflight emitted by a plurality of phosphors. Furthermore, if theabove-mentioned aluminate phosphor, halophosphate phosphor, etc. and theabove-mentioned phosphor layers (7) to (9) are used in combination, asemiconductor light-emitting device emits white light owing to the colormixture of light emitted by the light-emitting element 1 and lightemitted by the phosphor.

The semiconductor light-emitting device of the present embodiment uses aphosphor having an external quantum efficiency under the excitation ofthe blue light-emitting element that is not necessarily high and a highinternal quantum efficiency. Therefore, for example, in the case ofobtaining desired white light by the color mixture of light emitted bythe blue light-emitting element and light emitted by the phosphor, arelatively large amount of the phosphor is required. Thus, in order toobtain desired white light, it is necessary to increase the thickness ofa phosphor layer. On the other hand, when the thickness of the phosphorlayer increases, there is an advantage that a light-emitting device withless color irregularity of white light is obtained.

It is preferable that the phosphor layer 3 is composed of a plurality oflayers or a multi-layered configuration, and a part of the phosphorlayer 3 contains the above-mentioned nitride phosphor or oxynitridephosphor, since color blur and output blur of emitted light of thesemiconductor light-emitting device of the present embodiment can besuppressed.

A nitride phosphor or an oxynitride phosphor containing Eu²⁺ as aluminescent center ion absorbs blue, green, and yellow visible light toconvert it into red light. Therefore, when the phosphor layer 3containing the above-mentioned nitride phosphor or oxynitride phosphoris formed by mixing a blue phosphor, a green phosphor, or a yellowphosphor, and the above-mentioned nitride phosphor or oxynitridephosphor, the phosphor layer 3 absorbs light emitted by the blue, green,or yellow phosphor, whereby the nitride phosphor or oxynitride phosphoremits red light. Therefore, it becomes difficult to control the emissioncolor of the light-emitting device for the reason in terms of productionsteps of a phosphor layer. In order to solve this problem, it ispreferable that the phosphor layer 3 is composed of a plurality oflayers or a multi-layered configuration, and the layer closest to aprincipal light output surface of the light-emitting element 1 is madeof a nitride phosphor or an oxynitride phosphor emitting red light,whereby the phosphor layer 3 is made unlikely to be excited with lightemitted by the blue, green, or yellow phosphor. Furthermore, the yellowphosphor activated with Eu²⁺ or Ce³⁺ is excited with blue light or greenlight, and the above-mentioned green phosphor activated with Eu²⁺ orCe³⁺ is excited with blue light. Therefore, in the case where thephosphor layer 3 is formed by mixing a plurality of kinds of phosphorshaving different emission colors, the same problem as the above mayarise. In order to solve this problem, in the semiconductorlight-emitting device of the present embodiment, it is preferable thatthe phosphor layer 3 is composed of a plurality of layers or amulti-layered configuration, and the layer farthest from the principallight output surface of the light-emitting element 1 is made of aphosphor emitting light with a short wavelength.

The semiconductor light-emitting device of the present embodimentincludes at least the above-mentioned light-emitting element, and aphosphor layer having a high internal quantum efficiency under theexcitation of the light-emitting element and containing at least anitride phosphor or an oxynitride phosphor that converts excited lightinto red light efficiently, and provides, as output light, at least redlight-emitting component light emitted by the nitride phosphor oroxynitride phosphor. The semiconductor light-emitting device satisfiesboth a high luminous flux and a high color rendering property, and inparticular, emits white light in a warm color. In the case where thelight-emitting element is a blue light-emitting element, the outputlight further contains light-emitting component light emitted by thelight-emitting element.

FIGS. 4 and 5 are schematic views showing configurations ofillumination•display devices showing examples of the light-emittingdevice of the present invention. FIG. 4 shows an illumination•displaydevice configured using at least one semiconductor light-emitting device9 in which the phosphor layer 3 containing the above-mentioned phosphorcomposition 2 is combined with the light-emitting element 1, and outputlight 10 thereof. FIG. 5 shows an illumination•display device in whichat least one light-emitting element 1 is combined with the phosphorlayer 3 containing the above-mentioned phosphor composition 2, andoutput light 10 thereof. The same light-emitting element 1 and thephosphor layer 3 as those of the semiconductor light-emitting devicedescribed above can be used. Furthermore, the function, effect, and thelike of the illumination•display device with such a configuration alsoare the same as those in the case of a semiconductor light-emittingdevice described above.

FIGS. 6 to 12 show specific examples incorporating theillumination•display devices that are the embodiments of thelight-emitting device of the present invention schematically shown inFIGS. 4 and 5. FIG. 6 is a perspective view of an illumination module 12having an integrated light-emitting portion 11. FIG. 7 is a perspectiveview of the illumination module 12 having a plurality of light-emittingportions 11. FIG. 8 is a perspective view of a table lamp typeillumination device having a light-emitting portion 11 and being capableof controlling the ON-OFF and light amount with a switch 13. FIG. 9 is aside view of an illumination device as a light source configured using ascrew cap 14, a reflective plate 15, and an illumination module 12having a plurality of light-emitting portions 11. FIG. 10 is a bottomview of the illumination device shown in FIG. 9. FIG. 11 is aperspective view of a plate type image display device provided with thelight-emitting portions 11. FIG. 12 is a perspective view a segmentednumber display device provided with the light-emitting portions 11.

The illumination•display device of the present embodiment is configuredusing a phosphor having a high internal quantum efficiency under theexcitation of the light-emitting element, in particular, using asemiconductor light-emitting device with high intensity of a redlight-emitting component and a satisfactory color rendering property.Therefore, the illumination•display device satisfies a high luminousflux, and in particular a high color rendering property with a highintensity of a red light-emitting component, which are excellentrelative to those of the conventional illumination•display device.

As described above, according to the present invention, by combining atleast the above-mentioned nitride phosphor represented by a compositionformula: (M_(1-x)Eu_(x))AlSiN₃, with the light-emitting element, alight-emitting device that satisfies both a high luminous flux and ahigh color rendering property, in particular, a light-emitting deviceemitting white light in a warm color can be provided.

Furthermore, according to the present invention, by combining at least anitride phosphor or an oxynitride phosphor having an emission peak in awavelength range of 600 nm to less than 660 nm, an alkaline-earth metalorthosilicate phosphor having an emission peak in a wavelength range of500 nm to less than 600 nm, and the light-emitting element, alight-emitting device satisfying both a high luminous flux and a highcolor rendering property, in particular, a light-emitting deviceemitting white light in a warm color can be provided.

Hereinafter, the light-emitting device of the present invention will bedescribed in detail by way of examples.

Example 26

In the present example, a card-type illumination module light sourceshown in FIG. 41 was produced as a light-emitting device, and theemission characteristics thereof were evaluated. FIG. 42 is a partialcross-sectional view of FIG. 41.

First, a method for producing a semiconductor light-emitting device 44will be described. A blue LED chip 49 emitting light having an emissionpeak in the vicinity of 470 nm was mounted as a GaInN light-emittinglayer on paired n-electrode 46 and p-electrode 47 of respective Si diodeelements (submount elements) 45 formed in a matrix on an n-type Si wafervia a micro-bump 48.

The blue LED chip 49 was mounted on the respective Si diode elements 45formed in a matrix, and consequently, the blue LED chips 49 also weremounted in a matrix.

Then, the n-electrode 46 and the p-electrode 47 were connected to ann-electrode and a p-electrode of each blue LED chip 49. Thereafter, thephosphor layer 3 containing the phosphor composition 2 was formed on theperiphery of the blue LED chip 49 using a printing technique.Furthermore, the upper surface of the phosphor layer 3 was flattened bypolishing, and then, cut to be separated with a diamond cutter to form asemiconductor light-emitting device 44.

Next, a first insulating thick film 51 (thickness: 75 μm), a copperelectrode 52 (thickness: about 10 μm, width: 0.5 mm), a secondinsulating thick film 53 (thickness: 30 μm), and electrode pads 54 a and54 b (thickness: about 10 μm, 64 pairs in total) were laminatedsuccessively on an aluminum metal substrate 50 (size: 3 cm×3 cm,thickness: 1 mm), whereby a radiating multi-layered substrate 55 wasformed. The first insulating thick film 51 and the second insulatingthick film 53 were made of alumina-dispersed epoxy resin formed bythermocompression bonding. Furthermore, the copper electrode 52 waspatterned by etching, and the electrode pads 54 a and 54 b were positiveand negative electrodes for supplying power formed by etching. A contacthole was provided in a part of the second insulating thick film 53, andthe electrode pads 54 a and 54 b were formed so as to supply a currentthrough the copper electrode 52.

Next, the semiconductor light-emitting device 44 was disposed at apredetermined position on the radiating multi-layered substrate 55. Atthis time, a reverse electrode (n-electrode) 56 of the Si diode element45 was attached to the electrode pad 54 a with an Ag paste, and abonding pad portion 58 on the p-electrode 47 was connected to theelectrode pad 54 b with an Au wire 57, whereby a current can be suppliedto the semiconductor light-emitting device 44.

Next, an aluminum metal reflective plate 59 having a ground hole in theshape of a reverse conical tube was attached to the radiatingmulti-layered substrate 55 with an adhesive. At this time, thesemiconductor light-emitting device 44 on the radiating multi-layeredsubstrate 55 was formed so as to be housed in the ground hole of thealuminum metal reflective plate 59. Furthermore, a dome-shaped lens 60using epoxy resin was formed so as to cover the semiconductorlight-emitting device 44 and the entire ground hole, whereby thelight-emitting device of Example 26 was obtained.

FIG. 41 is a perspective view of the light-emitting device of Example26. In Example 26, a card-type illumination module light source wasproduced using 64 semiconductor light-emitting devices 44, and theemission characteristics thereof were evaluated.

In Example 26, a current of about 40 mA (about 80 mA in total) wasallowed to flow through two semiconductor light-emitting device groupseach having 32 semiconductor light-emitting devices 44 connected inseries to the copper electrodes 52, whereby the semiconductorlight-emitting devices 44 were driven to obtain output light. The outputlight is a color mixture of light emitted by the blue LED chip 49 andlight emitted by a phosphor contained in the phosphor layer 3, which isexcited with the light emitted by the blue LED chip to emit light.Furthermore, arbitrary white light was obtained as the output light byappropriately selecting the kind and amount of an LED chip and aphosphor.

Hereinafter, the phosphor layer 3 will be described.

The phosphor layer 3 was formed by hardening epoxy resin with a phosphoradded thereto by drying. In Example 26, two kinds of phosphors wereused: a SrASiN₃:Eu²⁺ red phosphor (center particle diameter: 2.2 μm,maximum internal quantum efficiency: 60%) having an emission peak in thevicinity of a wavelength of 625 nm and a (Ba, Sr)₂SiO₄:Eu²⁺ greenphosphor (center particle diameter: 12.7 μm, maximum internal quantumefficiency: 91%) having an emission peak in the vicinity of a wavelengthof 555 nm. As the epoxy resin, epoxy resin (main agent) mainlycontaining bisphenol A type liquid epoxy resin and two-solution mixedepoxy resin of epoxy resin (curing agent) mainly containing an alicyclicacid anhydride. The SrAlSiN₃:Eu²⁺ red phosphor and the (Ba,Sr)₂SiO₄:Eu²⁺ green phosphor were mixed in a weight ratio of about 1:10,and the mixed phosphor and the epoxy resin were mixed in a weight ratioof about 1:3 (phosphor concentration=25% by weight).

Comparative Example 6

A card-type illumination module light source was produced in the sameway as in Example 26, using two kinds of phosphors: a Sr₂Si₅N₈:Eu²⁺ redphosphor (center particle diameter: 1.8 μm, maximum internal quantumefficiency: 62%) having an emission peak in the vicinity of a wavelengthof 625 nm; and a Y₃Al₅O₁₂:Ce³⁺ yellow phosphor (center particlediameter: 17.6 μm, maximum internal quantum efficiency: 98%) having anemission peak in the vicinity of a wavelength of 560 nm. The phosphorlayer 3 was obtained by mixing a Sr₂Si₅N₈:Eu²⁺ red phosphor with aY₃Al₅O₁₂:Ce³⁺ yellow phosphor in a weight ratio of about 1:6, and mixingthe mixed phosphor thus obtained with epoxy resin in a weight ratio ofabout 1:14 (phosphor concentration 6.7% by weight). In the same way asin Example 26, output light was obtained by allowing a current to flowthrough the semiconductor light-emitting device, and the emissioncharacteristics thereof were evaluated.

The thickness of the phosphor layer 3 was set to be about 500 μm inExample 26, and about 100 μm in Comparative Example 6, in order toobtain white light with equal light color (relative color temperature:about 3800 K, duv, chromaticity). The emission characteristics of theSrAlSiN₃:Eu²⁺ red phosphor in Example 26 were originally similar tothose of the Sr₂Si₅N₈:Eu²⁺ red phosphor in Comparative Example 6. Forthe purpose of further enhancing the comparison precision, as thephosphor of Example 26, a green phosphor having emission performancethat is as similar as possible to that of Comparative Example 6 wasused. The (Ba, Sr)₂SiO₄:Eu²⁺ green phosphor in Example 26 and the (Ba,Sr)₂SiO₄:Eu²⁺ green phosphor shown in FIG. 32 are different from eachother in an atomic ratio of Sr and Ba, but similar to each other inexcitation wavelength dependency of an internal quantum efficiency andan external quantum efficiency.

Hereinafter, the emission characteristics of the light-emitting devicesof Example 26 and Comparative Example 6 will be described.

FIGS. 43 and 44 respectively show emission spectra in Example 26 andComparative Example 6. As is apparent from FIGS. 43 and 44, thelight-emitting devices of Example 26 and Comparative Example 6 havesimilar emission spectra, and emit white light having an emission peakin the vicinity of 470 nm and 600 nm, i.e., white light owing to thecolor mixture of blue light and yellow light.

Table 8 shows emission characteristics of the light-emitting devices ofExample 26 and Comparative Example 6

TABLE 8 Example 26 Comparative Example 6 Correlated color 3800 3797temperature (K) duv 0 −0.02 Chromaticity (x, y) (0.3897, 0.3823)(0.3898, 0.3823) Ra 83 83 R9 31 33 Relative luminous 98.7 100 flux

In Table 8, “duv” represents an index showing a shift of white lightfrom a blackbody radiation path. “Ra” represents an average colorrendering index, and “R9” represents a red special color renderingindex, which show how faithfully test light reproduces test color, withthe color seen in reference light being 100.

Under the condition of substantially equal light color (correlated colortemperature, duv, and chromaticity), irrespective of using a (Ba,Sr)₂SiO₄:Eu²⁺ green phosphor having low emission intensity under theillumination of light of 470 nm, Ra, R9, and luminous flux in Example 26were substantially similar to those in Comparative Example 6. That is,it was found that the emission performance in Example 16 was equal tothat in Comparative Example 6 (conventional light-emitting devicesatisfying both a high color rendering property and a high luminousflux). The reason for this is considered as follows: the internalquantum efficiency of the phosphor used in Example 26 under theirradiation of light emitted by the blue LED is high, the light emittedby the blue LED absorbed by the phosphor is converted efficiently toemit light, and light emitted by the blue LED that has not been absorbedis output efficiently.

The correlated color temperature of the light-emitting device can beadjusted arbitrarily by varying the concentration of the phosphor andthe thickness of the phosphor layer. The emission characteristics suchas a color rendering index and a luminous flux can be evaluated bysimulation, in the case where a phosphor layer is configured using atleast one phosphor having a predetermined spectral distribution and apredetermined internal quantum efficiency, and a base material such asresin with a transmittance of 100%, and a light-emitting device isconfigured using a light-emitting element with a constant output havinga predetermined spectral distribution, and the correlated colortemperature of output light is varied. When only a color rendering indexis evaluated, the numerical value of an internal quantum efficiency maynot be necessary, and the evaluation by simulation can be performed onlywith the spectral distribution of a phosphor and a light-emittingelement. In order to investigate the light color satisfying both thehigh color rendering property and the high luminous index of theabove-mentioned light-emitting devices, Ra and the behavior of arelative luminous flux of white light emitted by the light-emittingdevices of Example 26 and Comparative Example 6 were evaluated bysimulation, in the case of varying the correlated color temperature withduv being set to be 0.

FIG. 45 shows the results obtained by evaluating, by simulation, therelative luminous flux of white light emitted by the light-emittingdevices of Example 26 and Comparative Example 6 in the case of varying acorrelated color temperature. It is understood from FIG. 45 that similarbehaviors were exhibited in Example 26 and Comparative Example 6. Thatis, in the case of producing a light-emitting device with a correlatedcolor temperature of white light of 3000 K to 6000 K, preferably 3500 Kto 5000 K, Example 26 exhibits a relatively high luminous fluxcorresponding to 95 to 100% of a luminous flux in the case of settingthe correlated color temperature in Comparative Example 6 to be 3797K.The luminous flux in the case of setting the correlated colortemperature in Comparative Example 6 to be 3797K is represented by asolid line in FIG. 45.

Furthermore, FIG. 46 shows the results obtained by evaluating, bysimulation, the relative luminous flux of white light emitted by thelight-emitting devices of Example 26 and Comparative Example 6 in thecase of varying a correlated color temperature. It is understood thatrelatively high numerical values Ra of at least 80 were exhibited inExample 26 and Comparative Example 6 in the case of producing alight-emitting device with a correlated color temperature of white lightof 2000 K to 5000 K, preferably 2500 K to 4000 K.

It is understood from FIGS. 45 and 46 that, in Example 26 andComparative Example 6, in the case of producing a light-emitting devicewith a correlated color temperature of white light of 3000 K to 5000 K,preferably 3000 K to 4500 K, and more preferably 3500 K to 4000 K, alight-emitting device satisfying both a high luminous flux and high Rais obtained.

Example 27

A light-emitting device in which a correlated color temperature wasvaried with duv being set to be 0 was configured in the same way as inExample 26, except that the (Ba, Sr)₂SiO₄:Eu²⁺ green phosphor waschanged from a phosphor having an emission peak in the vicinity of awavelength of 555 nm to a phosphor having an emission peak in thevicinity of a wavelength of 535 nm.

FIG. 47 shows the results obtained by evaluating Ra of white lightemitted in Example 27 by simulation. It is understood from FIG. 47 thata light-emitting device with a lower correlated color temperatureexhibits higher Ra. In the case of producing a light-emitting deviceemitting white light with a correlated color temperature of 2000 K to5000 K, Ra is at least 80. Furthermore, in the case of a correlatedcolor temperature 3000 K or less, Ra is at least 90.

FIG. 48 shows the results obtained by evaluating R9 of white lightemitted by Example 27 by simulation. The following is understood fromFIG. 48. In the case of producing a light-emitting device emitting whitelight with a correlated color temperature of 2000 K to 8000 K, R9exhibits a high numerical value of at least 40. In the case of producinga light-emitting device emitting white light with a correlated colortemperature of 2500 K to 6500 K, R9 exhibits a numerical value of aboutat least 60. In the case of producing a light-emitting device emittingwhite light with a correlated color temperature of 3000 K to 5000 K, R9exhibits a numerical value of about at least 80.

FIG. 49 shows the results obtained by evaluating, by simulation, arelative luminous flux of white light emitted by the light-emittingdevice of Example 27 in the case of varying a correlated colortemperature. The following is understood from FIG. 49. In the case ofproducing a light-emitting device with a correlated color temperature ofwhite light of 2500 K to 8000 K, preferably 3000 K to 5000 K, and morepreferably 3500 K to 4500 K, in Example 27, a relatively high luminousflux is exhibited, which corresponds to 82% to 85% of the luminous fluxin the case where the correlated color temperature in ComparativeExample 6 is set to be 3797 K. The luminous flux in the case of settingthe correlated color temperature of Comparative Example 6 to be 3797 Kis represented by a solid line in FIG. 49.

It is understood from FIGS. 47 to 49 that the light-emitting device ofExample 27 emits output light with a high color rendering property,which has Ra and R9 of at least 80 and realizes a high luminous flux, inthe case where the correlated color temperature is 3000 K to 5000 K.Furthermore, the light-emitting device of Example 27 emits output lightwith a preferable color rendering property, which has Ra and R9 of atleast 82 and realizes a high luminous flux, in the case where thecorrelated color temperature is 3500 K to 4500 K. In particular, in thecase where the correlated color temperature is about 4000 K, thelight-emitting device emits output light with a more preferable colorrendering property, which has Ra and R9 of at least 85 and realizes ahigher luminous flux.

FIG. 50 shows the simulation data of an emission spectrum of thelight-emitting device of Example 27 emitting white light in a warm colorwith a particularly preferable correlated color temperature of 4000 K(duv=0). In the case of this emission spectrum, chromaticity (x, y) is(0.3805, 0.3768), and Ra and R9 are 86 and 95, respectively. The shapeof the emission spectrum represents a ratio in intensity of an emissionpeak in a wavelength range of 460 to 480 nm by a blue LED, an emissionpeak in a wavelength range of 520 to 550 nm by the green phosphor ofExample 27 emitting light based on a 5d-4f electron transition of rareearth ions, and an emission peak in a wavelength range of 610 to 640 nmby the red phosphor of Example 27 emitting light based on 5d-4f electrontransition of rare earth ions (i.e., 460-480 nm: 520-550 nm: 610-640 nmis 24-28: 12-15: 16-20). One preferable embodiment of the presentinvention is a light-emitting device that emits white light in a warmcolor having an emission spectrum shape in which an emission peak hasthe above-mentioned ratio. The phosphor emitting light based on 5d-4felectron transition of rare earth ions refers to a phosphor mainlycontaining rare earth ions such as Eu²⁺ or Ce³⁺ as a luminescent centerion. Such a phosphor has a similar emission spectrum shape irrespectiveof the kind of a phosphor host in the case where the wavelength of anemission peak is the same.

Furthermore, the following was found by simulation. In the case ofchanging the green phosphor of Example 26 to the (Ba, Sr)₂SiO₄:Eu²⁺green phosphor having an emission peak in a wavelength range of 520 to550 nm, and further adding the (Sr, Ba)₂SiO₄:Eu²⁺ yellow phosphor havingan emission peak in a wavelength range of 560 to 580 nm, alight-emitting device with a high color rendering property is obtained.For example, at output light with a correlated color temperature of 3800K, duv=0, and chromaticity (0.3897, 0.3823), Ra was 88, R9 was 72, and arelative luminous flux was 93%.

The relationship between the correlated color temperature, Ra, R9, andthe relative luminous flux was evaluated by simulation under the lightcolor condition where duv=0, in the case where the green phosphor ofExample 26 was changed to a (Ba, Sr)₂SiO₄:Eu²⁺ green phosphor having anemission peak in a shorter wavelength range of 520 nm, for example.Consequently, it was found that a light-emitting device with a shorterwavelength of an emission peak of a green phosphor has lower numericalvalues of Ra, R9, and relative luminous flux, and the performance as theillumination device decreases. For example, in the case of using a greenphosphor having an emission peak in a wavelength of 520 nm, at acorrelated color temperature of 3800 K, duv=0, and chromaticity (0.3897,0.3823), Ra was 80, R9 was 71, and the relative luminous flux was 85%.Thus, it is preferable to use a green phosphor with a wavelength of atleast 525 nm of an emission peak.

In Examples 26 and 27, the SrAlSiN₃:Eu²⁺ red phosphor was used. However,there is no particular limit thereto, as long as the phosphor is a redphosphor represented by a composition formula: (M_(1-x)Eu_(x))AlSiN₃,where “M” is at least one element selected from the group consisting ofMg, Ca, Sr, Ba, and Zn, and “x” is a numerical value satisfying0.005≦x≦0.3. For example, the same functional effect is recognized evenin the CaAlSiN₃:Eu²⁺ red phosphor.

Furthermore, even in the case of using, for example, a known nitridephosphor or oxynitride phosphor exhibiting similar emissioncharacteristics (e.g., a nitridosilicate phosphor represented by acomposition formula: (M_(1-x)Eu_(x))SiN₂ or a composition formula:(M_(1-x)Eu_(x))₂Si₅N₈, an oxonitridoaluminosilicate phosphor representedby a composition formula: (M_(1-x)Eu_(x))₂Si₄AlON₇) in place of theSrAlSiN₃:Eu²⁺ red phosphor, the similar functional effect is recognized.In the above-mentioned composition formula, “M” is at least one elementselected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and “x” isa numerical value satisfying 0.005≦x≦0.3.

Furthermore, the green phosphor and the yellow phosphor are not limitedto those used in the above-mentioned examples. It also is possible touse any phosphor emitting light having an emission peak in a wavelengthrange of 525 nm to less than 600 nm, for example, a phosphor having anexcitation peak on a longest wavelength side of an excitation spectrumin a wavelength range of less than 420 nm. Even when a YAG:Ce phosphorthat is known as a phosphor used for a white LED (e.g., a (Y₃(Al,Ga)₅O₁₂:Ce³⁺ green phosphor, a Y₃Al₅O₁₂:Ce³⁺ green phosphor, a (Y,Gd)₃Al₅O₁₂:Ce³⁺ yellow phosphor, a Y₃Al₅O₁₂:Ce³⁺, Pr³⁺ yellow phosphor)is used as the above-mentioned green phosphor or yellow phosphor, thesimilar functional effect is recognized.

Example 28

In the present example, a card-type illumination module light sourceshown in FIGS. 41 and 42 was produced by mounting a violet LED chipemitting light having an emission peak in the vicinity of 405, nm withGaInN being a light-emitting layer, in place of the blue LED chip 49described in Example 26 or 27, and the emission characteristics thereofwere evaluated. The output light of the present example was at leastmixed-color light mainly containing light emitted by a phosphor includedin the phosphor layer 3, which was excited with light emitted by theviolet LED chip to emit light. Furthermore, arbitrary white light wasobtained as the output light by appropriately selecting the kind andamount of the phosphor.

Hereinafter, the phosphor layer 3 of the present example will bedescribed in detail.

The phosphor layer 3 was formed by hardening epoxy resin with a phosphoradded thereto by drying. In the present example, three kinds ofphosphors were used: a SrAlSiN₃:Eu²⁺ red phosphor (center particlediameter: 2.2 μm, maximum internal quantum efficiency: 60%, internalquantum efficiency under the excitation of 405 nm: about 60%) having anemission peak in the vicinity of a wavelength of 625 nm, a (Ba,Sr)₂SiO₄:Eu²⁺ green phosphor (center particle diameter: 15.2 μm, maximuminternal quantum efficiency: 97%, internal quantum efficiency under theexcitation of 405 nm: about 97%) having an emission peak in the vicinityof a wavelength of 535 nm, and a BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (centerparticle diameter: 8.5 μm, maximum internal quantum efficiency: about100%, internal quantum efficiency under the excitation of 405 nm: about100%) having an emission peak in the vicinity of a wavelength of 450 nm.As the epoxy resin, two-solution mixed epoxy resin of epoxy resin (mainagent) mainly containing bisphenol A type liquid epoxy resin and epoxyresin (curing agent) mainly containing an alicyclic acid anhydride wasused. The production conditions for the above-mentioned SrAlSiN₃:Eu²⁺red phosphor have not been optimized. Therefore, although the internalquantum efficiency is low, it is possible to improve the internalquantum efficiency by at least 1.5 times by optimizing the productioncondition. The SrAlSiN₃:Eu²⁺ red phosphor, the (Ba, Sr)₂SiO₄:Eu²⁺ greenphosphor, and the BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor were mixed in a weightratio of about 6:11:30, and the mixed phosphor and epoxy resin weremixed in a weight ratio of about 1:3 (phosphor concentration 25% byweight).

Comparative Example 7

A card-type illumination module light source was produced in the sameway as in Example 28 using three kinds of phosphors: a La₂O₂S:Eu³⁺ redphosphor (center particle diameter: 9.3 μm, maximum internal quantumefficiency: 84%, internal quantum efficiency under the excitation of 405nm: about 50%) having an emission peak in the vicinity of a wavelengthof 626 nm, a (Ba, Sr)₂SiO₄:Eu²⁺ green phosphor (center particlediameter: 15.2 μm, maximum internal quantum efficiency: 97%, internalquantum efficiency under the excitation of 405 nm: about 97%) having anemission peak in the vicinity of a wavelength of 535 nm, and aBaMgAl₀₁O₁₇:Eu²⁺ blue phosphor (center particle diameter: 8.5 μm,maximum internal quantum efficiency: about 100%, internal quantumefficiency under the excitation of 405 nm: about 100%) having anemission peak in the vicinity of a wavelength of 450 nm. As the phosphorlayer 3, a La₂O₂S:Eu³⁺ red phosphor, a (Ba, Sr)₂SiO₄:Eu²⁺ greenphosphor, and a BaMgAl₀₁O₁₇:Eu²⁺ blue phosphor were mixed in a weightratio of about 155:20:33, and the mixed phosphor and epoxy resin weremixed in a weight ratio of about 1:3 (phosphor concentration=25% byweight). Then, in the same way as in Example 28, output light wasobtained by allowing a current to flow through the semiconductorlight-emitting device, and the emission characteristics thereof wereevaluated.

The thickness of the phosphor layer 3 was set to be about 500 μm inExample 28 and Comparative Example 7 so as to obtain white light withequal light color (correlated color temperature: about 3800 K, duv,chromaticity).

Hereinafter, the emission characteristics of the light-emitting devicesof Example 28 and Comparative Example 7 will be described.

FIGS. 51 and 52 respectively show emission spectra in Example 28 andComparative Example 7. As is understood from FIGS. 51 and 52, thelight-emitting devices in Example 28 and Comparative Example 7 emitwhite light having an emission peak in the vicinity of 405 nm, 450 nm,535 nm, and 625 nm, i.e., white light owing to the color mixture ofviolet light, blue light, green light, and red light. The emission peakin the vicinity of 405 nm represents the leakage of light of the violetlight-emitting element, and the emission peaks in the vicinity of 450nm, 535 nm, and 625 nm represent light obtained by converting theabove-mentioned violet light by the phosphors.

Table 9 shows the emission characteristics of the light-emitting devicesof Example 28 and Comparative Example 7.

TABLE 9 Example 28 Comparative Example 7 Correlated color 3800 3792temperature (K) Duv 0 0.03 Chromaticity (x, y) (0.3897, 0.3823) (0.3901,0.3826) Relative luminous 117 100 flux (%) Ra 96 78 R1 98 71 R2 97 93 R392 82 R4 93 67 R5 98 77 R6 98 85 R7 96 85 R8 95 66 R9 83 34 R10 92 91R11 90 62 R12 92 90 R13 99 77 R14 94 86 R15 97 71

In Table 9, “duv” represents an index showing a shift of white lightfrom a blackbody radiation path. “Ra” represents an average colorrendering index and “R1” to “R15” represent special color renderingindexes, which show how faithfully test light reproduces test color,with the color seen in reference light being 100. In particular, “R9” isa red special color rendering index.

In spite of the fact that production condition of the phosphor has notbeen optimized, and a low-performance red phosphor with a maximuminternal quantum efficiency of 60% is used, in Example 28, white lightwith a relative luminous flux higher by 17% than that of ComparativeExample 7 was emitted under the condition of substantially the samelight color (correlated color temperature, duv, and chromaticity). Themaximum internal quantum efficiency of a red phosphor used inComparative example 7 is 83%, so that the output efficiency of thelight-emitting device can be improved further by about 20%. In the caseof the red phosphor used in Example 28, the maximum internal quantumefficiency is 60%, so that there is a room for enhancing white output ofthe light-emitting device by at least about 65%. More specifically,theoretically, white light with a higher luminous flux will be emittedwith a material configuration of the light-emitting device of Example28.

Furthermore, in the case where the light-emitting device of Example 28was configured so as to emit white light with a correlated colortemperature of 3800 K by combining at least the above-mentionedphosphors, the light-emitting device thus configured exhibited Ra largerthan that of Comparative Example 7. Furthermore, in all the specialcolor rendering indexes R1 to R15, as well as R9, larger numericalvalues than those of Comparative Example 7 were obtained. This showsthat white light with a very satisfactory color rendering property isemitted in Example 28.

The light-emitting device of Example 28 emits white light having a highcolor rendering property in which the numerical values of the specialcolor rendering indexes R1 to R15 are at least 80, which is close to thesunlight. Such a light-emitting device is particularly suitable for amedical purpose. For example, an LED light source applicable to anendoscope or the like can be provided, and an excellent endoscope systemcapable of diagnosing under light close to the sunlight can be provided.

Hereinafter, in order to investigate the light color that satisfies boththe high color rendering property and the high luminous flux of theabove-mentioned light-emitting device, the results were obtained byevaluating, by simulation, Ra and the behavior of a relative luminousflux of white light emitted by the light-emitting devices of Example 28and Comparative Example 7, in the case of varying the correlated colortemperature with duv being set to be 0.

FIG. 53 shows the results obtained by evaluating, by simulation, arelative luminous flux of white light emitted by the light-emittingdevices of Example 28 and Comparative Example 7 in the case of varying acorrelated color temperature. It is understood from FIG. 53 that thelight-emitting device of Example 28 emits white light having a luminousflux higher by about 10 to 20% than that of Comparative Example 7 over awide correlated color temperature range of 2000 K to 12000 K.Furthermore, it is understood that the light-emitting device of Example28 shows a relatively high luminous flux corresponding to at least 110to 115% level of a luminous flux in the case of setting the correlatedcolor temperature to be 3792 K in Comparative Example 7, when alight-emitting device with a correlated color temperature of outputlight of 2500 K to 12000 K, preferably 3500 K to 7000 K. The luminousflux in the case of setting the correlated color temperature ofComparative Example 7 is represented by a solid line in FIG. 53.

Hereinafter, regarding the respective phosphors used in Example 28 andComparative Example 7, assuming that the production condition issufficiently optimized and a phosphor with a maximum internal quantumefficiency of 100% is obtained, the results obtained by evaluating, bysimulation, a luminous flux in the case of using this ideal phosphorwill be described. In this simulation, the internal quantum efficiencyunder the excitation of 405 nm of each phosphor was estimated andevaluated from FIGS. 30, 32, 37, and 40, as shown in the following Table10.

TABLE 10 Phosphor Internal quantum efficiency (%) SrAlSiN₃:Eu²⁺ redphosphor 100 La₂O₂S:Eu³⁺ red phosphor 60 (Ba,Sr)₂SiO₄:Eu²⁺ greenphosphor 100 BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor 100

FIG. 54 shows the results obtained by evaluating, by simulation, arelative luminous flux of white light emitted by the light-emittingdevices of Example 28 and Comparative Example 7 in the case of varying acorrelated color temperature, when using the ideal phosphor. It isunderstood from FIG. 54 that, in the case of using the ideal phosphor,the light-emitting device of Example 28 emits white light with aluminous flux higher by about 45 to 65% than that in Comparative Example7 over a correlated color temperature range of 2000 K to 12000 K.Furthermore, in the case of producing a light-emitting device with acorrelated color temperature of white light of 2500 K to 12000,preferably 3500 K to 6000 K, the light-emitting device thus producedexhibits a relatively high luminous flux corresponding to at least 150to 160% of a luminous flux in the case of setting the correlated colortemperature to be 3792 K in Comparative Example 7. The luminous flux inthe case of setting the correlated color temperature of ComparativeExample 7 to be 3792 K is represented by a solid line in FIG. 54.

More specifically, depending upon the future enhancement of performanceof a SrAlSiN₃:Eu²⁺ red phosphor, it can be expected that alight-emitting device emitting a luminous flux higher by about 45 to 65%than that in Comparative Example 7 is obtained under the evaluation ofthe same correlated color temperature.

FIG. 55 shows the results obtained by evaluating, by simulation, anaverage color rendering index (Ra) of white light emitted by thelight-emitting devices of Example 28 and Comparative Example 7 in thecase of varying a correlated color temperature. It is understood thatthe light-emitting device of Example 28 exhibits high Ra of at least 90over a wide correlated color temperature range of 2000 K to 12000 K of acorrelated color temperature of white light, and exhibits very high Raof at least 95 over a wide correlated color temperature range of 3000 Kto 12000 K.

FIG. 56 shows the results obtained by evaluating, by simulation, a redspecial color rendering index (R9) of white light emitted by thelight-emitting device of Example 28 and Comparative Example 7 in thecase of varying a correlated color temperature. The light-emittingdevice of Example 28 with a correlated color temperature of 2500 K to12000 K shows a numerical value of R9 larger than that in ComparativeExample 7. Furthermore, the light-emitting device exhibits high R9 of atleast 30 over a wide correlated color temperature of white light of 2000K to 12000 K, at least 70 in a range of 3000 K to 12000 K, at least 80in a range of 3500 K to 12000 K, and at least 90 in a range of 5000 K to12000 K. Thus, a preferable light-emitting device emitting white lighthaving a high red color rendering index is obtained. The maximum value(96 to 98) of R9 was obtained in a correlated color temperature range of6000 K to 8000 K.

It is understood from FIGS. 53 to 55 that the light-emitting device ofExample 28 emits white light with a higher luminous flux and higher Rathan those in Comparative Example 7 over a wide correlated colortemperature range of 2000 K to 12000 K. Furthermore, it is understoodthat, in the case of producing a light-emitting device with a correlatedcolor temperature of white light of 2500 K to 12000 K, preferably 3500 Kto 7000 K, and more preferably 4000 K to 5500 K, a light-emitting devicethat satisfies both a high luminous flux and high Ra can be obtained.

Furthermore, it is understood from FIGS. 53 to 56 that thelight-emitting device of Example 28 emits white light with a higherluminous flux and higher R9 than those of Comparative Example 7 over awide correlated color temperature range of 2500 K to 12000 K.Furthermore, in the case of producing a light-emitting device with acorrelated color temperature of white light of 3000 K to 12000 K,preferably 3500 K to 12000 K, more preferably 5000 K to 12000 K, andmost preferably 6000 K to 8000 K, a light-emitting device that satisfiesboth a high luminous flux and high R9 is obtained.

FIG. 57 shows simulation data of an emission spectrum of thelight-emitting device of Example 28 that emits white light in a warmcolor with a correlated color temperature of 4500 K (duv=0) having aparticularly preferable luminous flux and Ra. In the case of thisemission spectrum, chromaticity (x, y) is (0.3608, 0.3635); Ra is 96; R1is 98; R2 and R6 to R8 are 97; R3, R10, and R11 are 91; R4 and R14 are94; R5, R13, and R15 are 99; and R9 and R12 are 88. It is understoodthat this can provide a light-emitting device emitting white lighthaving a satisfactory color rendering property with all the specialcolor rendering indexes of R1 to R15 being at least 85. The shape ofthis light-emitting spectrum represents a ratio in intensity of anemission peak in a wavelength range of 400 to 410 nm by a violet LED andan emission peak in a wavelength range of 440 to 460 nm, 520 to 540 nm,and 610 to 640 nm by a RGB phosphor in Example 28 emitting light basedon 5d-4f electron transition of rare earth ions (i.e., 400-410 nm:440-460 nm: 520-540 nm: 610-640 nm is 8-10: 12-14: 15-17: 16-18). Onepreferable embodiment of the present invention is a light-emittingdevice that emits white light in a warm color having an emissionspectrum shape in which an emission peak has the above-mentioned ratio.The phosphor emitting light based on 5d-4f electron transition of rareearth ions refers to a phosphor mainly containing rare earth ions suchas Eu²⁺ or Ce⁸⁺ as a luminescent center ion. Such a phosphor has asimilar emission spectrum shape irrespective of the kind of a phosphorhost in the case where the wavelength of an emission peak is the same.

FIG. 58 shows simulation data of an emission spectrum of thelight-emitting device of Example 28 emitting white light with acorrelated color temperature of 5500 K (duv=0) having a particularlypreferable luminous flux and Ra. In the case of this emission spectrum,chromaticity (x, y) is (0.3324, 0.3410); Ra is 96; R1 and R13 are 98;R2, R8, and R15 are 97; R3 and R12 are 90; R4 is 92; R5 is 99; R6 is 96;R7 is 95; R9 and R14 are 94; and R10 and R11 are 91. More specifically,according to the present invention, it also is possible to provide, forexample, a light-emitting device that emits white light close to thesunlight suitable for a medical purpose, with all the special colorrendering indexes R1 to R15 being at least 90. The shape of thisemission spectrum represents a ratio in intensity of an emission peak ina wavelength range of 400 to 410 nm by a violet LED and an emission peakin a wavelength range of 440 to 460 nm, 520 to 540 nm, and 610 to 640 nmby an RGB phosphor of Example 28 emitting light based on 5d-4f electrontransition of rare earth ions (i.e., 400-410 nm: 440-460 nm: 520-540 nm:610-640 nm is 4-6: 9-11: 8-10: 7-9). One preferable embodiment of thepresent invention is a light-emitting device emitting white light havingan emission spectrum shape in which an emission peak has theabove-mentioned ratio.

In Example 28, the case has been described where the light-emittingdevice is composed of a combination of a violet LED and three kinds ofred, green, and blue (RGB) phosphors, and SrAlSiN₃:Eu²⁺ is used as a redphosphor. Even in the case where the light-emitting device is configuredby combining at least the above-mentioned violet LED with a phosphorrepresented by a composition formula: (M_(1-x)Eu_(x)AlSiN₃ such asSrAlSiN₃:Eu²⁺ or CaAlSiN₃:Eu²⁺, and four kinds of red, yellow, green,and blue (RYGB) phosphors or three kinds of red, yellow, and blue (RYB)phosphors are used, the same function and effect are recognized.

Furthermore, in Example 28, the case using a SrAlSiN₃:Eu²⁺ red phosphorhas been described. However, the present invention is not limitedthereto, as long as a phosphor is represented by a composition formula:(M_(1-x)Eu_(x))AlSiN₃, where “M” is at least one element selected fromthe group consisting of Mg, Ca, Sr, Ba, and Zn, and “x” is a numericalvalue satisfying 0.005≦x≦0.3. Furthermore, a green phosphor is notlimited to that used in the above example, as long as it is a greenphosphor emitting light having an emission peak in a wavelength range of500 nm to less than 560 nm. A yellow phosphor emitting light having anemission peak in a wavelength range of 560 nm to less than 600 nm may beused in place of the green phosphor. The above-mentioned green or yellowphosphor having preferable emission output is the one activated withEu²⁺ or Ce³⁺.

The characteristics of the SrAlSiN₃:Eu²⁺ red phosphor are similar tothose of the conventional red phosphors, for example, a nitride phosphoror an oxynitride phosphor such as SrSiN₂:Eu²⁺, Sr₂Si₅N₈:Eu²⁺, orSr₂Si₄AlON₇:Eu²⁺. Therefore, even in the case of using theabove-mentioned conventional nitride phosphor or oxynitride phosphor inplace of a SrAlSiN₃:Eu²⁺ red phosphor in Example 27 or 28, the samefunctional effect is recognized.

Hereinafter, for reference, a method for producing SrAlSiN₃:Eu²⁺,Sr₂Si₅N₈:Eu²⁺, SrSiN₂:Eu²⁺, (Ba, Sr)₂SiO₄:Eu²⁺ (emission peak: 555 nm),(Ba, Sr)₂SiO₄:Eu²⁺ (emission peak: 535 nm), (Ba, Sr)₂SiO₄:Eu²⁺ (emissionpeak: 520 nm), and (Sr, Ba)₂SiO₄:Eu²⁺ (emission peak: 570 nm), among theabove-mentioned phosphors, will be described. As the Y₃Al₅O₁₂:Ce³⁺yellow phosphor, the La₂O₂S:Eu³⁺ red phosphor, and the BaMgAl₁₀O₁₇:Eu²⁺blue phosphor, those which are available commercially were used.

Tables 11 and 12 show the mass of material compounds used for producingeach phosphor.

TABLE 11 Phosphor ingredient (g) Phosphor Sr₃N₂ Si₃N₄ AlN Eu₂O₃SrAlSiN₃:Eu²⁺ 10.000 4.291 4.314 0.370 Sr₂Si₅N₈:Eu²⁺ 10.000 12.303 00.370 SrSiN₂:Eu²⁺ 10.000 4.291 0 0.370

TABLE 12 Phosphor ingredient (g) Phosphor BaCO₃ SrCO₃ SiO₂ Eu₂O₃(Ba,Sr)₂SiO₄:Eu²⁺ 386.457 183.348 100.000 11.480 (Peak: 520 nm)(Ba,Sr)₂SiO₄:Eu²⁺ 257.638 279.847 100.000 11.480 (Peak: 535 nm)(Ba,Sr)₂SiO₄:Eu²⁺ 128.819 376.345 100.000 11.480 (Peak: 555 nm)(Sr,Ba)₂SiO₄:Eu²⁺ 32.205 448.719 100.000 11.480 (Peak: 570 nm)

A method for producing three kinds of red phosphors shown in Table 11will be described. First, predetermined compounds shown in Table 11 weremixed in a dry nitrogen atmosphere with a glove box, a mortar, etc. toobtain mixed powder. At this time, an accelerant (flux) was not used.Next, the mixed powder was placed in an alumina crucible. The mixedpowder was fired provisionally in a nitrogen atmosphere at 800° C. to1400° C. for 2 to 4 hours, and fired in an atmosphere of 97% nitrogenand 3% hydrogen at 1600° C. to 1800° C. for 2 hours to synthesize a redphosphor. After the firing, the body color of the phosphor powder wasorange. After the firing, predetermined aftertreatments such aspulverizing, classification, washing, and drying were performed toobtain a red phosphor.

Next, a method for producing four kinds of green phosphors and yellowphosphors shown in Table 12 will be described. First, predeterminedcompounds shown in Table 12 were mixed in the atmosphere with a mortarto obtain mixed powder. Then, the mixed powder was placed in an aluminacrucible. The mixed powder was fired provisionally in the atmosphere at950° C. to 1000° C. for 2 to 4 hours to obtain provisionally firedpowder. As a flux, 3.620 g of calcium chloride (CaCl₂) powder was addedto the provisionally fired powder and mixed therewith. Thereafter, theresultant powder was fired in an atmosphere of 97% nitrogen and 3%hydrogen at 1200° C. to 1300° C. for 4 hours, whereby a green phosphorand a yellow phosphor were synthesized. The body color of the phosphorpowder after the firing was green to yellow. After the firing,predetermined aftertreatments such as pulverizing, classification,washing, and drying were performed to obtain a green phosphor and ayellow phosphor.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not limiting. The scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

The phosphor composition of the present invention contains a compositionrepresented by a composition formula: aM₃N₂.bAlN.cSi₃N₄ as a maincomponent of a phosphor host. In the composition formula, “M” is atleast one element selected from the group consisting of Mg, Ca, Sr, Ba,and Zn, and “a”, “b”, and “c” are numerical values respectivelysatisfying 0.2≦a/(a+b)≦0.95, 0.05≦b/(b+c)≦0.8, and 0.4≦c/(c+a)≦0.95. Inparticular, the phosphor composition of the present invention contains acomposition represented by a composition formula: MAlSiN₃ as a maincomponent of a phosphor host. Therefore, a novel phosphor can beprovided, which is capable of being excited with ultravioletlight-near-ultraviolet light-violet light-blue light-green light-yellowlight-orange light, in particular, red light in a warm color.

Furthermore, according to a method for producing a phosphor compositionof the present invention, a material containing a compound capable ofgenerating an oxide of the above-mentioned element “M” by heating, asilicon compound, an aluminum compound, a compound containing an elementforming a luminescent center ion, and carbon is allowed to react in anitriding gas atmosphere. Therefore, the phosphor composition of thepresent invention can be produced using an inexpensive material that iseasy to handle without using a nitride of alkaline-earth metal oralkaline-earth metal that is unstable chemically, difficult to handle inthe atmosphere, and expensive. Thus, a novel nitride phosphorcomposition having satisfactory material performance can be industriallyproduced at a low cost.

Furthermore, the light-emitting device of the present invention isconfigured using, as a light-emitting source, the above-mentioned novel,high-performance, and inexpensive phosphor composition of the presentinvention that emits light in a warm color, in particular, red light.Therefore, a light-emitting device (LED light source, etc.) can beprovided, which has a high red light-emitting component intensity andhigh performance, and is inexpensive and novel in terms of the materialconfiguration.

Furthermore, according to the present invention, a light-emitting deviceemitting white light can be provided, which satisfies both a high colorrendering property and a high luminous flux. In particular, alight-emitting device such as an LED light source can be provided, whichemits white light in a warm color and has a high emission intensity of ared light-emitting component.

1. A light-emitting device comprising: a phosphor layer containing a redphosphor having an emission peak in a wavelength range of 600 nm to lessthan 660 nm, and a green phosphor having an emission peak in awavelength range of 510 nm to 550 nm; and a blue light-emitting elementthat emits blue light having an emission peak in a wavelength range of440 nm to less than 500 nm, the red phosphor and the green phosphorbeing excited with the blue light to emit light, the blue light that hasnot been absorbed by the phosphor being transmitted through the phosphorlayer to be output, and output light containing a light-emittingcomponent emitted by the red phosphor, a light-emitting componentemitted by the green phosphor, and a light-emitting component emitted bythe blue light-emitting element, wherein the phosphor layer does notsubstantially contain a phosphor other than a phosphor activated withEu²⁺ or Ce³⁺, the red phosphor is a nitridoaluminosilicate-basedphosphor activated with Eu²⁺, the green phosphor is any of an aluminatephosphor activated with Eu²⁺ and a phosphor with a garnet structureactivated with Ce³⁺, having an excitation peak in a wavelength rangeshorter than a blue range with a wavelength of 440 nm to less than 500nm, and a phosphor having a lowest internal quantum efficiency under theexcitation of light emitted by the blue light-emitting element among thephosphors contained in the phosphor layer is a phosphor having aninternal quantum efficiency of at least 85%.
 2. The light-emittingdevice according to claim 1, wherein the blue light-emitting element hasan emission peak in a wavelength range of 450 nm to 480 nm.
 3. Thelight-emitting device according to claim 1, wherein the red phosphor hasan excitation peak in a wavelength range shorter than a blue range witha wavelength of 440 nm to less than 500 nm.
 4. The light-emitting deviceaccording to claim 1, wherein the phosphor with a garnet structureactivated with Ce³⁺ is any phosphor selected from the group consistingof Y₃(Al, Ga)₅O₁₂:Ce³⁺, Y₃Al₅O₁₂:Ce³⁺, BaY₂SiAl₄O₁₂:Ce³⁺, andCa₃Sc₂Si₃O₁₂:Ce³⁺.
 5. The light-emitting device according to claim 1,wherein the red phosphor is a phosphor represented by a compositionformula: (M_(1-x)Eu_(x))AlSiN₃, the M is at least one element selectedfrom the group consisting of Mg, Ca, Sr, Ba, and Zn, and the x is anumerical value satisfying an expression: 0.005≦x≦0.3.
 6. Thelight-emitting device according to claim 5, wherein at least 50 atomic %of the M of the red phosphor is Sr.
 7. The light-emitting deviceaccording to claim 1, wherein the green phosphor has an emission peak ina wavelength range of at least 525 nm.
 8. The light-emitting deviceaccording to claim 1, wherein a correlated color temperature of theoutput light is 2500 K to 8000 K.